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SO U TH ATLANTIC 0 A LIVING MARINE 0 VOLUME I "Id vopi 45, QH 91 .8 34 6L S'722 74w DISCLAIMER This report has been reviewed by the Bureau of Land Management and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the Bureau, nor does mention of trade names or commercial products constitute endorsement or recommenda- tion for use. FINAL REPORT SOUTH ATLANTIC OCS AREA LIVING MARINE RESOURCES STUDY VOLUME I AN INVESTIGATION OF LIVE BOTTOM HABITATS SOUTH OF CAPE FEAR, NORTH CAROLINA Prepared for Bureau of Land Management Washington, D. C. under Contract AA551-CT9-27 Prepared by Marine Resources Research Institute South Carolina Wildlife and Marine Resources Department Charleston, South Carolina and Coastal Resources Division Georgia Department of Natural Resources Brunswick, Georgia October 1981 gee &-amazy DEPARTMENT OF COMMERCE NOAA COASTAL SERVICES CENTER 2234 SOUTH 908SON AVENUE CHARLESTON , SC 2@05-2W TABLE OF CONTENTS EXECUTIVE SUMMARY PAGE BACKGROUND AND OBJECTIVES OF THE STUDY ................................ 1 STUDY AREAS ........................................................... SAMPLING METHODOLOGY .................................................. GENERAL RESULTS AND CONCLUSIONS ....................................... 3 METHODOLOGY EVALUATION AND RECOMMENDATIONS FOR FUTURE STUDIES ......... 6 REPORT ORGANIZATION ................................................... 7 REFERENCE CITED ....................................................... 8 VOLUME I LIST OF TABLES ........................................................ xii LIST OF FIGURES ....................................................... xvii ABSTRACT .............................................................. xxvii CHAPTER 1 , * 1 Background ....................................................... 1 Project Organization ............................................. 2 Project Participants ........ 0 ............................... 3 South Carolina Marine Resources Research Institute ....... 3 Georgia Coastal Resources Division ....................... 3 Project Management .......................................... 3 General Objectives and Scope ..................................... 5 CHAPTER 2 SAMPLING APPROACH AND METHODS .............................. 6 Introduction ..................................................... 6 Location of Study Areas .......................................... 6 Sampling Periods ................................................. Sampling Methods ................................................. 9 Research Vessels and Navigation ............................. 9 Hydrographic and Meteorological Methods ..................... 9 Physical Habitat Characterization ........................... 9 Underwater Television Transects .......................... 9 PAGE Still Camera Transects ................................... 10 Diver Surveys ............................................ 12 Rock Samples ............................................. 12 Biological Community Characterization ....................... 12 Trawl Sampling ........................................... 12 Baited Fishing Gear ...................................... 13 Juvenile Fish Sled ....................................... 13 Television and Still Camera Transects .................... 13 Diver Swimming Transects ................................. 13 Dredge Sampling .......................................... 14 Suction Sampling ......................................... 14 Grab Sampling ............................................ 15 CHAPTER 3 HYDROGRAPHY AND WEATHER OBSERVATIONS ....................... 16 Introduction ..................................................... 16 Laboratory Methods ................................................ 16 Results .......................................................... 16 Water Temperature ....................................... o ... 16 Salinity .................. o ................................. 18 Dissolved Oxygen ......o ..................................... 18 Light Transmission ................... o..................... o 22 Light Penetration ........................................... 22 Meteorological Observations ............................. o ... 22 Discussion .................. o .................................... 22 Impact/Enhancement ............................................... 24 Conclusions ........................ o ............................. 24 CHAPTER 4 PHYSICAL HABITAT CHARACTERIZATION .......................... 25 Introduction ..................................................... 25 Methods of Laboratory Analysis ................................... 25 Television Transects ........................................ 25 Fathometer Readings ......................................... 26 Still Camera Transects ...................................... 26 Rock Analysis .............................. o ................ 26 Results .......................................................... 27 Description of the Study Sites ..................... o ........ 27 Inner Shelf Stations ..................................... 27 Middle Shelf Stations ............................... o .... 31 Outer Shelf Stations ..................................... 31 Substratum Analysis ......................................... 36 Rock Analyses ............................................... 41 Discussio n....... o ........ o........................ o ......... o ... 44 PAGE Impact/Enhancement ............................................... 49 Conclusions ...................................................... 49 1 51 CHAPTER 5 BENTHIC COMMUNITY .......................................... Introduction ..................................................... 51 Methods .......................................................... 51 Laboratory Analysis ......................................... 51 Television Transects ..................................... 51 Still Camera Transect Analysis ........................... 52 Removal Sampling Gears ................................... 52 Data Analysis ............................................... 53 Television Transects ..................................... 53 Removal Sampling Gears ..... o ............................. 53 Numerical Classificationo ................................ 53 Nodal Analysis ........................................... 55 Reciprocal Averaging Ordination .......................... 55 Species Diversity- ..................................... 56 Species Abundance ............. o..................... o .... 57 Biomass .................................................. 57 Results .......................................................... 57 Assessment of Epibenthos by Television Transects ............ 57 Assessment of Epibenthos by Still Camera Transects ......... 59 Qualitative Assessment of Epibenthos Captured by Dredge and Trawl Sampling ................. o ........................ 67 Species Composition .......................... o ........... 67 Biomass .................................................. 72 Species Assemblages and Distributional Patterns: Dredge Collections ................................... o ... 72 Species Assemblages and Distributional Patterns: Trawl Collections ..................................... 88 Quantitative Assessment of Benthos Captured by Suction and Grab Samplers., ...................... o .................. 100 Species Composition and Abundance... ..... o ............... 100 Community Structure ...................................... 115 Species Assemblages and Distributional Patterns- ....... o 116 Discussion ....................................................... 140 Diversity of the Live Bottom Communities .................... 140 Community Composition ................................... o ... 144 Dominance ........................ oo ......................... 147 Biomass ..................................................... 148 Impact/Enhancement ............................................... 141 Conclusions ...................................................... 151 CHAPTER 6 NEKTONIC COMMUNITY ......................................... 153 Introduction ..................................................... 153 iv PAGE Methods .......................................................... 153 Laboratory Analysis ......................................... 153 Trawl Collections ........................................ 153 Underwater Television Transects .......................... 153 Diver Observations ....................................... 154 Baited Fishing Gear ...................................... 154 Juvenile Fish Sled ....................................... 154 Data Analysis ............................................... 154 Biomass .................................................. 154 Abundance ................................................ 155 Numerical Classification ................................. 155 Dominance and Diversity .................................. 156 Results .......................................................... 156 Quantitative Assessment of Fish Captured by Trawl ........... 156 Species Composition and Abundance ........................ 156 Biomass .................................................. 176 Diversity ................................................ 176 Cluster Analysis ......................................... 185 Fishes Observed or Collected by Other Gear .................. 200 Underwater Television .................................... 200 Diver Photographs and Swimming Transects ................. 200 Baited Fishing Gear ...................................... 207 Assessment of Larval and Juvenile Fishes ................. 212 Discussion ....................................................... 226 Impact/Enhancement ............................................... 233 Conclusions ...................................................... 234 CHAPTER 7 FOOD HABITS OF FISHES ...................................... 236 Introduction ..................................................... 236 Methods .......................................................... 236 Laboratory Analysis ......................................... 236 Data Analysis ............................................... 237 Results .......................................................... 238 Centropristis striata ....................................... 238 Pagrus pagrus ............................................... 238 Rhomboplites aurorubens ..................................... 238 Calamus leucosteus .......................................... 251 Stenotomus aculeatus ........................................ 251 Lutjanus campechanus ........................................ 251 Mycteroperca microlepis ..................................... 251 Overlap in Diet ............................................. 263 Habitat of Prey Items ....................................... 263 Discussion ....................................................... 263 Impact/Enhancement ............................................... 269 Conclusions ...................................................... 271 v PAGE CHAPTER 8 METHODOLOGY EVALUATION AND RECOMMENDATIONS FOR FUTURE STUDIES ................... t ................................. 273 Methodology Evaluation ........................................... 273 Remate Censusing Gears ...................................... 273 Television Transects ..................................... 273 Still Camera Transects ................................... 273 Removal Sampling Gears ...................................... 273 Trawl .................................................... 274 Baited Fishing Gears ..................................... 274 Fish Sled ................................................ 274 Dredges .................................................. 275 Suction Sampler and Smith-McIntyre Grab .................. 275 Diver Assessments and Swimming Transects ................. 276 Recommendations for Future Research ......................... 276 ACKNOWL]EDGEMENTS ...................................................... 280 REFERENCES CITED ...................................................... 284 VOLUME II LIST OF TABLES ........................................................ xii LIST OF FIGURES ....................................................... xiv ABSTRACT .............................................................. xvii CHAPTER 1 INTRODUCTION ............................................... 1 1 Project Organization ............................................. 2 General Information ......................................... 2 Management Structure ........................................ 2 Cruise Participants ......................................... 4 General Objectives...... ......................................... 4 Areas Sampled ............................................... 4 Time Sampled ................................................ 5 Gear Employed ............................................... 5 CHAPTER 2 SAMPLING APPROACH AND METHODS .............................. 6 Location of Study Areas .......................................... 6 Inner Shelf Site ............................................ Middle Shelf Site ........................................... Outer Shelf Site ............................................ 8 Sampling Periods ................................................. 8 vi PAGE Sampling Methods ................................................. 8 Research Vessels and Navigation ............................. 8 Hydrographic and Meteorological Methods ..................... 8 Physical Habitat Characterization ........................... 9 Biological Community Characterization ....................... 10 OW4ER 3 HYDROGRAPHY AND WEATHER OBSERVATIONS ....................... 12 Introduction ..................................................... 12 Laboratory Methods ............................................... 12 Results .......................................................... 12 Discussion ....................................................... 12 Impact/Enhancement ............................................... 15 Conclusions ...................................................... 15 CHAPTER 4 PHYSICAL CHARACTERIZATION OF STUDY AREAS ................... 16 Introduction ..................................................... 16 Methods ........................................................... 16 Results .......................................................... 17 Inner Shelf Station ......................................... 17 Diver Observations ....................................... 17 Fathometer Transects ..................................... 17 Middle Shelf Station ........................................ 17 Diver Observations ....................................... 17 Fathometer Transects ..................................... 17 Television Reconnaissance and Transects .................. 17 Outer Shelf Station ......................................... 24 Fathometer Transects ..................................... 24 Television Reconnaissance and Transects .................. 24 Discussion ....................................................... 24 Impact/Enhancement ............................................... 27 Conclusions ...................................................... 27 CHAPTER 5 BENTHIC COMMUNITY .......................................... 29 Introduction ..................................................... 29 Methods .......................................................... 29 Laboratory Analysis .......................................... 29 Data Analysis ............................................... 30 Results .......................................................... 32 Diver Observations .......................................... 32 IS04 ..................................................... 32 MS04 ..................................................... 32 vii PAGE Television Transect Analysis ................................ 32 Dredge and Trawl Sampling ................................... 32 Species Composition ...................................... 32 Biomass Distribution ..................................... 37 Community Composition .................................... 37 Suction and Grab Sampling ................................... 41 Species Composition and Abundance ........................ 41 Species and Dominance Diversity .......................... 52 Community Composition .................................... 52 Discussion ....................................................... 60 Impact/Enhancement ................................................ 66 Conclusions ...................................................... 67 CHAPTER 6 NEKTONIC COHMUNITY ......................................... 68 Introduction ..................................................... 68 Methods .......................................................... 68 Laboratory Analysis ......................................... 68 Trawl Collections ........................................ 68 Underwater Television Transects .......................... 68 Diver Observations ....................................... 68 Baited Fishing Gear ...................................... 68 Data Analysis ............................................... 69 Abundance ................................................ 69 Biomass .................................................. 69 Dominance and Diversity .................................. 69 Cluster Analysis ......................................... 69 70 Quantitative Assessment of Fish Captured by Trawl ........... 70 Species Composition and Abundance ........................ 70 Biomass .................................................. 70 Diversity and Dominance .................................. 76 Cluster Analysis ......................................... 76 Fishes Observed or Collected by Other Gear .................. 76 Underwater Television .................................... 76 Diver Observations ....................................... 82 Baited Fishing Gear ...................................... 82 Discussion ....................................................... 82 Impact/Enhancement ............................................... 91 Conclusions ...................................................... 9@ CHAPTER 7 FOOD HABITS AND TROPHIC RELATIONSHIPS OF FISHES ............ 93 Introduction ..................................................... 93 viii PAGE Methods .......................................................... 93 Laboratory Analysis ......................................... 93 Data Analysis ............................................... 94 Results .......................................................... 94 Centropristis striata ....................................... 94 Haemulon plumieri ........................................... 94 Haemulon aurolineatum ....................................... 94 Stenotomus aculeatus ........................................ 94 Discussion ................................. 4 ..................... 106 Impact/Enhancement ............................................... 107 Conclusions ........................................ o.......... 107 CHAPTER 8 METHODOLOGY EVALUATION AND RECOMMENDATIONS FOR FUTURE STUDIESo ..................................... o............. 109 Methodology Evaluation .................... o ........o............. 109 Suction Sampling .............................. o......... o ... 109 Grab Sampling.... ........................................... 109 Dredge Sampling ............................................. 109 Television Transect Sampling ................................ 109 Trawl Sampling .............................................. 112 Rod and Reel Sampling ....................................... 112 Fish Trap Sampling .......................................... 112 Longline Sampling .......................................... o 114 Juvenile Fish Sampling ...................................... 114 Recommendations for Future Studies ...... o................. o ...... 114 ACKNOWLEDGEMENTS .................... o ................................. 116 REFERENCES CITED ....................................................... 117 VOLUME III PREFACE ............................................................... xii APPENDICES FOR VOLUME I ............................................... 1 Appendix 1. Field records obtained for each sample collection during the winter cruise 1980 ....................... 2 Appendix 2. Field records obtained for each sample collection during the summer cruise 1980 ....................... 14 Appendix 3. Temperature readings (*C) obtained from reversing and bucket thermometers at live bottom stations sampled during winter and summer cruises, 1980 ...... 25 ix PAGE Appendix 4. Salinity measurements (0/oo) obtained from hydrocasts at live bottom stations sampled during winter and summer cruises, 1980 ............. 26 Appendix Dissolved oxygen measurements (ml 1-1) obtained from hydrocasts at live bottom stations sampled during winter and summer cruises, 1980. Values in ( ) represent the % saturation values for surface and bottom samples ......................... 27 Appendix 6. Light transmission measurements (%) obtained using the transmissometer and Secchi disc read- ings from live bottom stations during winter and summer cruises, 1980 ........................... 29 Appendix 7. Data format used to facilitate anaiysis of epibenthic communities at live bottom stations ..... 30 Appendix 8. Phylogenetic list of invertebrate taxa collected by dredge at each station during winter (w) and summer (s), 1980 ................................... 31 Appendix 9. Phylogenetic list of invertebrate taxa collected by trawl at each station during winter (w) and summer (s), 1980 ................................... 44 Appendix 10. Ranked abundance of invertebrate and macroalgae species collected by suction and grab samplers at each station during winter, 1980 * Averne (2) density, expressed as number per 0.10 m , and standard error (SE) are indicated .............. 56 Appendix 11. Ranked abundance of invertebrate and macroalgae species collected by suction and grab samplers at each station during summer, 1980. Averafe (R) density, expressed as number per 0.10 m , and standard error (SE) are indicated .............. 91 Appendix 12, Community structure values [number of individualst number of speciest Shannon diversity (H'), even- ness W), and richness (SR)] for invertebrates in each suction (stations IS01-MS03) and grab (stations OS01-OS03) collection during winter, 1980 ............................................... 125 Appendix 13. Community structure values [number of individuals number of species, Shannon diversity (H'), even- ness (J') and richness (SR)] for invertebrates in each suction (stations IS01-MS03) and grab (stations OS01-OS03) collection during summer, 1980 ............................................... 127 x Appendix 14. Abundance by station of fish species captured PAGE by trawl for winter (w) and summer (s) ............. 129 Appendix 15. Community structure values (number of individuals, number of species, Shannon diversity (H'), evenness W), and richness (SR)] for fish in each trawl collection during winter, 1980 ..................... 135 Appendix 16. Community structure values (number of individuals, number of species, Shannon diversity (H'), evenness W), and richness (SR)] for fish in each trawl collection during summer, 1980 ..................... 137 Appendix 17. Abundance of individual taxa of larval,and juvenile fishes by station and season ........................ 139 APPENDICES FOR VOLUME II .............................................. 144 Appendix 18. Field records obtained for each collection during the simmker cruise 1980 ............................. 145 Appendix 19. Species list of invertebrates and algae collected in two dredge samples at station IS04 for summer 1980 ............................................... 149 Appendix 20. Species list of invertebrates and algae collected in two dredge samples at station NS04 for summer 1980 ............................................... 150 Appendix 21. Species list of invertebrates and algae collected in two dredge samples at station OS04 for summer 1980 ............................................... 152 Appendix 22. Species list of invertebrates and;algae collected i in six trawl samples at station MS04 for summer 1980 ............................................... 153 Appendix 23. Mean weights (shown as grams + 1 SE) of major taxonomic groups collected usling a rock dredge (N = 2) and trawl (N = 6) at ISO4, MS04, and OS04 during summer 1980 sampling effort ................. 154 Appendix 24. Species list of invertebrates and algae collected in five airlift suction samples at station IS04 for simmer 1980 .................................... 155 Appendix 25. Species list of invertebrates and algae collected in five airlift suction samples at station MS04 for summer 1980 .................................... 156 Appendix 26. Species list of invertebrates and algae collected in five Smith-McIntyre grab samples at station OS04 for summer 1980 ............................... 158 xi PAGE Appendix 27. Species diversity (H'), species evenness W), and species richness for demersal fishes caught by trawl in summer 1980 ..................... 159 Appendix 28* Abundance by station of fish species captured by trawl (N - 6 per station) off North Carolina for summer 1980 .................................... 160 Appendix 29. Reduced temperature and dissolved oxygen data by depth at three stations off North Carolina for summer 1980 .................................... 162 Appendix 30. Bibliography for Volumes I and II .................. 163 xii LIST OF TABLES CHAPTER TWO PAGE fable 2. 1. Location of the live bottom stations sampled in winter and summer, 1980 ............................................... 8 CHAPTER FOUR Table 4. 1. Depths recorded by fathometer during television transects .................................................. 28 4. 2. Results of thin section analysis and general description of rocks collected by dredges and SCUBA divers at live bottom stations ............................................ 42 CHAPTER FIVE Table 5. 1. Percent frequency of occurrence for the hard corals Oculina sp. and Solenastrea hyades, and for macroalgae (undetermined), based on television transect analysis at live bottom stations ....................................... 61 5. 2. Results from point count analysis of O.5-m2 photographic quadrats taken 1 m above bottom showing percent cover of selected taxa .............................................. 62 5. 3. List of taxa identified in 0.5-m 2 photographic quadrats taken 1 m above bottom ...................... 0 .............. 63 5. 4. Estimated mean (-X) densities and standard deviation (S.D.) of selected species observed in 3-m2 photographic quadrats taken 3 m above bottom ..................................... 64 5. 5. Invertebrate species represented in 15 or more dredge collections from both winter and summer, 1980 ..... o ....... 68 5. 6. Invertebrate species represented in 15 or more trawl collections from both winter and summer, 1980 ..... 0.... t... 69 5. 7. Numbers of species and percent of total numbers for major taxonomic groups represented in dredge collections at each station and sampling period ........................ 70 xiii PAGE Table 5. 8. iumbers of species and percent of total number for major taxonomic groups represented in trawl collections at each station and sampling period ........................ 71 5. 9. Percent of the total biomass for major taxonomic groups in dredge collections for each station and sampling period ..................................................... 75 5.10. Percent of the total biomass for major taxonomic groups in trawl collections for each station and sampling period ..................................................... 76 5.11. Species groups resulting from numerical classification of data from samples collected by dredge during winter and summer, 1980 ............................ # .................. 82 5.12. Species groups resulting from numerical classification of data from samples collected by trawl during winter and summer, 1980 ............................................... 94 5.13. Numerical ranking of invertebrate species collected by suction and grab samplers ................................. 102 5.14. Community structure values (number of individuals, number of species, Shannon diversity (H'), evenness (J'), and richness (SR)] for pooled replicate samples of inverte- brates at each station during winter and summer, 1980 ...... 118 5.15. Species groups resulting from numerical classification of data from samples collected by suction and grab samplers during winter and summer, 1980 ............ .................. 135 CHAPTER SIX Table 6. 1. Ten most abundant demersal fish species in winter and summer 1980, all stations combined ......................... 157 6. 2. Ten most abundant demersal fish species, in winter 1980, by station ............................................. 0 ... 1584 t 6. 3. Ten most abundant demersal fish species, in summer 1980, by station ....................................... 0 ......... 161 xiv PAGE Table 6. 4. Abundance of dominant and priority species by season and light phase ................................................ 166 6. 5. Abundance estimates for trawl-caught demersal teleosts during winter and summer, 1980 ............................. 181 6. 6. Abundance estimates for trawl-caught nekton (pelagic and demersal fishes and squids) during winter and summer, 1980 ....................................................... 182 6. 7. Biomass estimates for trawl-caught demersal teleosts during winter and summer, 1980 ............................. 183 6. 8. Biomass estimates for trawl-caught nekton (pelagic and demersal fishes and squids) during winter and summer, 1980 ....................................................... 184 6. 9. Abundance of fishes counted at each station on videotape transects during winter, 1980 .............................. 201 6.10. Abundance of fishes counted at each station on videotape transects during simmer, 1980 .............................. 203 6.11. Abundance estimates (number of individuals ha-1) of selected species, based on television and trawl analysis ... 205 6.12. Abundance of fishes seen in photographs taken by divers using the still camera during winter and summer, 1980 ... 0.. 206 6.13. Abundance of fishes seeen by divers along swimming transects during winter and summer, 1980 ................... 208 6.14. Abundance of fish species caught on vertical longlines during winter and summer, 1980 ............................. 209 6.15. Abundance of fish species caught on snapper reels during 210 winter and summer, 1980 .................................... 6.16. Abundance of fish species caught in Antillean S-traps during winter and summer, 1980 ............................. 211 6.17. Abundance of fish species caught in rectangular Antillean traps during summer, 1980 ............................... o.. 213 6.18. Five most abundant families of larval and juvenile fishes collected by fish sled at each station during winter, 214 1980 ....................................................... 6.19. Five most abundant families of larval and juvenile fishes collected by fish sled at each station during summer, 1980 ........... o ........................................... 216 xv PAGE Table 6.20. Average (R) minimum and maximum values and range of standard length (SL) for larval and juvenile fishes col- lected in winter, 1980 ..................................... 218 6.21. Average (30 minimum and maximum values and range of standard length (SL) for larval and juvenile fishes col- lected in summer, 1980 .................................. oo. 221 6.22. Number of individuals and number of taxa of larval and juvenile fishes in fish sled collections, winter 1980.... o. 224 6.23. 'Numbers of individuals and number of taxa of larval and juvenile fishes in fish sled collections, summer 1980., .... 225 CHAPTER SEVEN Table 7. 1. Percent frequency occurrence (F), percent number (N), percent volume (V), and index of relative importance (IRI) of food items in Centropristis striata stomachs for both sampling periods ....... o....o .............................. 240 7, 2* Percent frequency occurrence (F), percent number (N), percent volume (V), and index of relative importance (IRI) of food items in Pagrus pagrus stomachs for both sampling periods... o.oo.oo .... oo ......... o....... o..o ............... 245 7. 3. Percent frequency occurrence (F), percent number (N), percent volume (V), and index of relative importance (IRI) of food items in Rhomboplites aurorubens stomachs for both sampling periods... * .... *..* .......... *0 ...........0 ..... 0. 249 7. 4. Percent frequency occurrence (F), percent number (N), percent volume (V), and index of relative importance (IRI) of food items in Calamus leucosteus stomachs for both sampling periods ........................................... 253 7. 5. Percent frequency occurrence (F), percent number (N), percent volume (V), and index of relative importance (IRI) of food items in Stenotomus aculeatus stomachs for both sampling periods ........................................... 257@', 7. 6. Percent frequency occurrence (F), percent number (N), percent volume (V), and index of relative importance (IRI) of food items in LutJanus campechanus stomachs for both sampling periods ........................................... 261 xvi PAGE Table 7. 7. Percent frequency occurrence (F), percent number (N), percent volume (V), and index of relative importance (IRI) of food items in Mycteroperca microlepis stomachs for both sampling periods ........................................... 262 CHAPTER EIGHT Table 8. 1. Index of dispersion (I, Elliott 1977) and estimated number of samples (n) needed to obtain an estimate of the popula- tion mean within + 40% of the true value for the ten numerically dominant invertebrate species in suction and grab samples ......................... 0 ..................... 277 ACKNOWLEDGEMENTS Table 9. 1. Project personnel from South Carolina Marine Resources Research Institute and their areas of responsibility ....... 281 9. 2. Project personnel from Georgia Coastal Resources Division and their areas of responsibility .......................... 283 xvii LIST OF FIGURES CHAPTER ONE PAGE Figure 1. 1. General project organization depicting the integrated management structure of South Carolina MRRI and Georgia CRD personnel .................................................. 4 CHAPTER TWO Figure 2. 1. Location and depth zones of live bottom stations sampled during winter and summer, 1980 ............................. 7 2. 2. Schematic diagrams of two frames (A and B) used for tele- vision and still camera transects .......................... CHAPTER THREE Figure 3. 1. Vertical profiles of water temperature (OC) at live bottom stations during winter and summer, 1980 .................... 17 3. 2. Vertical profiles of salinity (0/oo) and dissolved oxygen (ml 1-1) at inner shelf stations during winter and summer, 1980 ....................................................... 19 0/oo) and dissolved oxygen 3. Vertical profiles of salinity ( (ml 1-1) at middle shelf stations during winter and summer, 1980 ....................................................... 20 S. 4. Vertic1l profiles of salinity (0/oo) and dissolved oxy gen (ml 1- ) at outer shelf stations during winter and summer, 1980 ....................................................... 21 3. 5. Vertical profiles of light transmission at live bottom stations during winter*and summer, 1980 .................... 23 CHAPTER FOUR Figure 4. 1. Location of television transects at Station IS01 ........... 29 4. 2. Location of television transects at Station IS02 ........... 30 xviii PAGE Figure 4. 3. Location of television transects at Station IS03 ........... 32 4. 4. Location of television transects at Station MS01 ......... 33 4. 5. Location of television transects at Station MS02 ........... 34 4. 6. Location of television transects at Station MS03 ........... 35 4. 7. Location of television transects at Station OS01 ........... 37 4. 8. Location of television transects at Station OS02 ........... 38 4. 9. Location of television transects at Station OS03 ........... 39 4.10. Mean percent frequency of live bottom from videotape analysis of the study sites ................................ 40 4.11. A live bottom station with typical low relief hard ground covered by an extensive layer of sand ...................... 45 4.12. A live bottom station with patchy outcroppings of low relief ..................................................... 46 4.13. A ledge of moderate relief at a live bottom station ........ 47 CHAPTER FIVE Figure 5. 1. Frequency of three sponge species along television transects during winter and summer, 1980 ............................. 58 5. 2. Frequency of coral along television transects during winter and summer, 1980 ............................ o .............. 60 5. 3. Number of species collected at each station by dredge during winter and summer, 1980 ........................... 73 5. 4. Number of species collected by trawl at each station during winter and summer, 1980 .................................... 74 5. 5. Normal cluster dendrogram of winter dredge collections indicating station groups formed using the Jaccard simi- larity coefficient and flexible sorting ..................... 77 5. 6. Normal cluster dendrogram of summer dredge collections indicating station groups formed using the Jaccard simi- larity coefficient and flexible sorting .................... 78 xix PAGE Figure 5. 7. Results of reciprocal averaging ordination showing orienta- tion of winter dredge collections at stations on axes 1 and 2.......................................................... 80 5. 8. Results of reciprocal averaging ordination showing orienta- tion of summer dredge collections at stations on axes 1 and 2.......................................................... 81 5. 9. inverse classification hierarchies and nodal diagram showing constancy and fidelity of station - species group coincidence based on winter dredge collections ............. 84 5.10. inverse classification hierarchies and nodal diagram showing constancy and fidelity of station - species group coincidence based on summer dredge collections ............. 86 5.11. Matrix showing co-occurrence of species within the same group formed by inverse cluster analysis of dredge col- lections from winter sampling only, summer sampling only, or both winter and summer sampling ......................... 87 5.12. Normal cluster dendrogram of winter trawl collections indi- cating station groups formed using the Jaccard similarity coefficient and flexible sorting ........................... 89 5.13. Normal cluster dendrogram of summer trawl collections indi- cating station groups formed using the Jaccard similarity coefficient and flexible sorting ........................... 90 5..14. Results of reciprocal averaging ordination showing orienta- tion of winter trawl collections at stations on axes 1 and 2.......................................................... 91 5.15. Results of reciprocal averaging ordination showing orienta- tion of summer trawl collections at stations on axes 1 and 2.......................................................... 92 5.16. Inverse classification hierarchies and nodal diagram showing constancy and fidelity of station - species group coinci- dence based on winter trawl collections .................... 97 5.17. Inverse classification hierarchies and nodal diagram showing constancy and fidelity of station - species group coinci- dence based on summer trawl collections .................... 9 8 5.18. Matrix showing co-occurrence of species within the same group formed by inverse cluster analysis of trawl col- lections from winter sampling only, simmer sampling only, or both winter and summer sampling ......................... 99 xx PAGE Figure 5.19. Relative abundance of FilMrana implexa during winter and summer, 1980 ............................................... 105 5.20. Relative abundance of Phyllochaetopterus socialis during winter and summer, 1980... ......... 00 ...................... 106 5.21. Relative abundance of Spiophanes bombyx during winter and summer, 1980 .................... o .......................... 107 5o22. Relative abundance of Exo&one dispar during winter and summer, 1980 ........... o ......... o ......................... 108 5.23o Relative abundance of Syllis spongicola during winter and simmer, 1980 ...................... - ...................... 109 5.24. Relative abundance of Photis sp. during winter and summer, 1980 ...................... ............. o ............ 110 5o25. Relative abundance of Podocerus sp. during winter and summer, 1980 ............. 0............... o ........ oo ....... ill 5.26. Relative abufidance of Luconacia incerta during winter and summer, 1980 ....... o..... oo ............................. o.. 112 5.27. Relative Abundance of Erichthonius sp. A during winter and summer, 1980 .......... o .................................... 113 5.28. Relative abundance of Ophiothrix angulata during winter and summer, 1980 .................. o...oo .... o.* ................ 114 5.29o Shannon diversity (H') for pooled replicate samples of invertebrates at each station during winter and.sioner, 1980 ......................... o....... o................ o..o. 117 5.30. Scatterplot showing Shannon diversity (H') in relation to sampling depth.... 119 5.31. Dominance diversity curve and dominance index (D.I.) values for invertebrates collected by the suction sampler at station IS01 during 1980, .................... o........... oo 120 5.32. Dominance diversity curve and dominance index (D.I.) values for invertebrates collected by the suction sampler at station IS02 during 1980. .................... o......... 121 5.33. Dominance diversity curve and dominance index (D.I.) values for invertebrates collected by the suction sampler at station IS03 during 1980 ....... o ........................... 122 xxi PAGE Figure 5.34. Dominance diversity curve and dominance index (D.I.) values for invertebrates collected by the suction sampler at station MS01 during l980 ................................... 123 5.35. Dominance diversity curve and dominance index (D.I.) values for invertebrates collected by the suction sampler at station MS02 during 1980.4 ................................. 124 5.36. Dominance diversity curve and dominance index (D.I.) values for invertebrates collected by the suction sampler at station MS03 during 1980 ................................... 125 5.37. Dominance diversity curve and dominance index (D.I.) values for invertebrates collected by the grab sampler at station OS01 during 1980 ........................................... 126 5.38. Dominance diversity curve and dominance index (D.I.) values for invertebrates collected by the grab sampler at station OS02 during 1980 .......................................... 127 5.39. Dominance diversity curve and dominance index (D.I.) values for invertebrates collected by the grab sampler at station OS03 during 1980 ........................................... 128 5.40. Normal cluster dendrogram of winter suction and grab col- lections indicating station groups formed by a combination of Canberra metric similarity coefficient, square root transformation, and flexible sorting ....................... 130 5.41. Normal cluster dendrogram of summer suction and grab col- lections indicating station groups formed using the Canberra metric similarity coefficient, square root trans- formation, and flexible sorting ...... * .................... 131 5.42. Results of reciprocal averaging ordination showing orienta- tion of winter suction and grab collections at stations on axes 1 and 2 ............................................... 132 5.43. Results of reciprocal averaging ordination showing orienta- tion of summer suction and grab collections at stations on axes 1 and 2 ............................................... 133 5.44. Inverse classification hierarchies and nodal diagram showing constancy and fidelity of station - species group coincidence based on winter suction and grab collections ... 138 5.45. Inverse classification hierarchies and nodal diagram showing constancy and fidelity of station - species group coincidence based on summer suction and grab collections... 139 xxii PAGE Figure 5.46. Matrix showing co-occurrence of species within the same group formed by inverse cluster analysis of suction and grab collections taken during winter sampling only, summer sampling only, or both winter and summer sampling .......... 141 CHAPTER SIX Figure 6. 1. Relative abundance of Stenotomus aculeatus during winter and summer, 1980 .......................................... 164 6. 2. Relative abundance of Haemulon aurolineatum. during winter and summer, 1980 ........................................... 167 6. 3. Relative abundance of Rhomboplites aurorubens during winter and summer, 1980 ..................................... 0 ..... 168 6. 4. Relative abundance of Equetus lanceolatus during winter and summer, 1980 ........................... o............. 0 ..... 169 6. 5. Relative abundance of Centropristis striata during winter and summer, 1980 .............................. 0 ............ 170 6. 6. Relative abundance of Prionotus carolinus during winter and 171 simmer, 1980 ............................................... 6. 7. Relative abundance of Calamus leucosteus during winter and 172 summer, 1980 ................................................ 6. 8. Relative abundance of Equetus umbrosus during winter and 173 summer, 1980 ............................................... 6. 9. Relative abundance of Urophycis regia during winter and 174 summer, 1980... o ........................................... 6.10. Relative abundance of Monacanthus hispidus during winter 175 and simmer, 1980 ........................................... 6.11. Relative abundance of Lutjanus campechanus during winter 177 and summer, 1980 ........ o..o ......... o.o.o ......... oo ...... 6.12. Relative abundance of Mycteroperca. microlepis during winter and summer, 1980 .......... o ....................... o .... O.o. 178 6.13. Relative abundance of Pagrus pagrus during winter and summer, 1980. .............. o ............................... 179 iii PAGE Fig-are 6.14. Relative abundance of demersal teleosts collected during winter and summer, 1980 .................................... 180 6.15. Shannon diversity (H') for pooled replicate samples of demersal fishes at each station, by light phase and season. 186 6.16. Shannon diversity (H') for pooled replicate samples of demersal fishes at each station during winter and summer, 1980 ....................................................... 187 6.17. Species richness (SR) for pooled replicate samples of demersal fishes at each station during winter and summer, 1980 ....................................................... 188 6.18. Dominance diversity curves and dominance index (D.I.) values for demersal fishes collected at inner shelf stations during 1980 sampling ....................................... 189 6.19. Dominance diversity curves and dominance index (D.I.) values for demersal fishes collected at middle and outer shelf stations during 1980 sampling ............. 9 ................ 190 6.20. Normal cluster dendrogram of winter trawl collections of demersal fishes ....... -6-ees-eso-eoseoeoswe .... O.o 191 6..21o Normal cluster dendrogram of summer trawl collections of demersal fishes ....... *oeoooeooeo*oooooooeo*oooooloooooeooe 192 6.22o Inverse cluster dendrogram of winter trawl collections of demersal fishes ...... 194 6.23o Inverse classification hierarchies and nodal diagram showing constancy and fidelity of station - species group coincidence based on winter collections of demersal fishes .............. oo9ooooooooo*oooooooooooooooo*ooooo*ooo 195 6.24. Inverse classification hierarchies and nodal diagram showing constancy and fidelity of station - species group coincidence based on winter collection of demersal fishes. Stations are separated into day and night collections ..... o 196 6.25. Inverse cluster dendrogram of summer trawl collections of demersal fishes .......... oq...oq.q.qoqoqoq*qoqlqoqoqoqoqoqoqoqoqoqeqoqlqeqeqoqsqeqsqoqoqo 198q? 6.26. Inverse classification hierarchies and nodal diagram showing constancy and fidelity of station - species group coincidence based on summer collections of demersal fisheso 198 xxiv PAGE Figure 6.27. Inverse classification hierarchies and nodal diagram showing constancy and fidelity of station - species group coincidence based on summer collections of demersal fishes. Stations are separated into day and night collections ...... 199 6.28. Collection locations for larval and juvenile priority fish species captured by fish sled ......................... 227 CHAPTER SEVEN Figure 7. 1. Frequency, number, volume (percents) and index of relative importance (IRI) of higher taxonomic groups of food in the diet of Centropristis striata .............................. 239 7. 2. Frequency, number, volume (percents) and index of relative importance (IRI) of higher taxonomic groups of food in the diet of Pagrus pagrus ...................................... 244 7. 3. Frequency, number, volume (percents) and index of relative importance (IRI) of higher taxonomic groups of food in the diet of Rhomboplites aurorubens.. ...... 0 ................... 248 7. 4. Frequency, number, volume (percents) and index of relative importance (IRI) of higher taxonomic groups of food in the diet of Calamus leucosteus ........ o.......... *9 ............ 252 7. 5. Frequency, number, volume (percents) and index of relative importance (IRI) of higher taxonomic groups of food in the diet of Stenotomus aculeatus... ...... o ..................... 256 7. 6. Frequency, number, volume (percents) and index of relative importance (IRI) of higher taxonomic groups of food in the diet of Lutjanus campechanus ............................... 260 7. 7. Dendrograms depicting overlap in diet among predators ...... 264 7. 8. Diet overlap between predators as measured by the Bray- Curtis similarity measure .................................. 265 7. 9. Percent of total volume of food consisting of live bottom organisms, sand bottom organisms, water column organisms or prey for which habitat is unknown .................. qr .... 266 7.10. Schematic food web depicting alternate food sources for live bottom fishes.. ....................................... 270 xxv CHAPTER EIGHT PAGE Figure 8. 1. ipecies accumulation curves for invertebrates at stations sampled by suction and grab during winter and summer, 1980.. 278 xxvi ABSTRACT Major objectives of this study were to (1) characterize benthic and nektonic communities associated with representative live bottom habitats on the continental shelf of the South Atlantic Bight, and (2) evaluate factors which might influence these communities, particularly the potential for impact by offshore oil and gas activities. Nine live bottom areas assessed during winter and summer of 1980 were located off South Carolina, Georgia and Florida between latitudes 30' and 330N and in water depths representing inner (19 - 27 m), middle (28 - 55 m), and outer (56 - 100 m) shelf zones. Sampling gears used at each study site included underwater televi- sion and still camera systems, fathometers, Niskin bottle casts with reversing thermometers, a transmissometer, scuba, trawl, fish traps, vertical long lines, snapper reels, an epibenthic juvenile fish sled, dredges, a Smith-McIntyre grab, and a suction sampler. Hydrographic measurements obtained were typical of the South Atlantic Bight. Water temperature was the most variable parameter, particularly at inner !shelf sites. Salinity and dissolved oxygen were generally high and water clarity, as measured by the transmissometer, showed no consistent pattern. Assessment of bottom topography documented differences in relief among study areas, ranging from areas of hard bottom with low rock relief (< 0.5 m) to areas with rock outcroppings of moderate to high relief (0.5 - > 2 m). Live bottom within most study areas was patchy, and all but one area, located in middle shelf waters off northern Florida, had roughly similar proportions of live versus non-live bottom. Invertebrate communities at all study sites were very diverse relative to sand bottom areas, but algae were generally sparse. No consistent patterns were noted in diversity with respect to depth, latitude, or season. Species composition of invertebrates, on the other hand, changed with depth and, to some extent, with season, but generally not with latitude. Most species collected at the study areas represented Carolinian and Tropical fauna. Invertebrate biomass was generally dominated by sponges; however,the occurrence of large sponges and octocorals decreased with increasing depth. Community composition of demersal fishes collected at the study areas also varied with depth and season. Highest fish biomass and high concentrations of commercially valuable species were collected at middle shelf sites. Diversity of demersal fish catches was greatest at the outer shelf and was most stable seasonally in this depth zone. Food habits analysis of commercially mportant species indicated that Centropristis striata and Pagrus pagrus fed heavily on live bottom fauna, Rho@m_b_oplites aurorubens fed on invertebrates in the water column, and Lutjanus campechanus and Mycteroperca microlepis were top carnivores. Two other abundant demersal species, Calamus leucosteus and Stenotomus aculeatus, ingested a mixture of fauna from sand and live bottom habitats. Detrimental impacts from offshore drilling operations are dependent on depth, currents, and distance of platforms (or discharge points) from live bottom areas. Negative impacts should be minimized or avoided by restrictin platform placement (or discharge of cuttings and drilling muds) to distances- of at least 1000 m from live bottom habitat. Positive impacts from drilling and production platforms would result from the creation of artificial reefs which should enhance fish density. xxvii Based on the limited information obtained in the first year of this study, recommended research efforts include increased seasonal sampling and food habits analysis of selected demersal species, recolonization and growth rate studies, and monitoring studies if oil rigs are placed near live bottom habitat. CHAPTER 1 INTRODUCTION BACKGROUND In. order to meet the growing demands for petroleum products in the United States, the Department of Energy has accelerated its efforts to locate and extract hydrocarbon resources beneath the ocean floor. The Southeastern Georgia Embayment was opened for exploration by Lease Sale 43 in 1978, and exploration associated with this lease sale has already started. Further, Lease Sales 56 and 78 are scheduled for the South Atlantic Bight in 1981 and 1984, respectively. Due to distinct geologic and stratigraphic features, outcroppings of sedimentary rock have been associated historically with potential energy reserves. Correspondingly, areas of prime interest resulting from Outer Continental Shelf Lease Sale 43 and areas nominated for Lease Sales 56 and 78 often coincide with the scattered occurrences of biologic assemblages associated with hard bottom locations. These rocky outcroppings are unique areas consisting of very rich and productive infaunal, epifaunal, and demersal assemblages of invertebrate and vertebrate species. For the purpose of this study, hard or "live" bottom areas are defined as areas containing "biological assemblages consisting of such sessile invertebrates as sea fans, sea whips, hydroids, anemones, ascidians, sponges, bryozoans, or corals living upon and attached to naturally occurring hard or rocky formations with rough, broken, or smooth topography, or whose lithotope favors the accumulation of turtles, fishes, and other fauna" (U. S. Department of Interior 1981). Five different types of live bottom *areas have already been identified in the South Atlantic Bight. They consist of (1) the shelf break (Eddy et al. 1967, 1,1acintyre and Milliman 1970),(2) a relict lithothamnion reef off North Carolina (Menzies et al. 1966), (3) coral outcroppings (Huntsman and Macintyre 1971), (4) Black Rocks (Pearse and Williams 1951), and (5) Gray's Reef off Georgia (Hunt 1974; U. S. Department of Commerce, Office of Coastal Zone Management 1980). These habitats are interspersed throughout the relatively smooth sand bottom of the South Atlantic continental shelf area and can be separated into three bathymetric zones. The first is a relatively shallow water zone (approximately 19 - 27 m) that exists near shore. Known locally as "black fish banks" (Bearden and McKenzie 1971), this area typifies a number of inshore areas off South Carolina, Georgia,and North Carolina. Further offshore, in waters of approximately 28 - 55 m, occur the so-called "snapper banks" and other reefs of a similar discontinuous nature. The third and deepest zone is found at the edge of the continental shelf in depths of approximately 56 - 100 m. This shelf edge habitat is more or less continuous along the entire shelf off the Florida, Georgia, South Carolina, and North Carolina coasts. Al: present, little is known regarding the areal extent or geographical distribution of these biologically important habitats; nor is there a compre7 hensive understanding of the biological communities which inhabit them. Eveh at Grail's Reef, which has been studied in greater detail than any other live bottom area on the South Carolina-Georgia Shelf (Hunt 1974), little quantita- tive data exists on the community structure, population sizes, or species 2 composition of the diverse groups of organisms that inhabit these biologically sensitive areas. Nevertheless, the importance of live bottom reefs to the commercial and recreational fisheries of the South Atlantic Region has been well documented (Cummins et al. 1962, Menzies et al. 1966, Struhsaker 1969, Bearden and McKinzie 1971, Sekavec and Huntsman 1972, Miller and Richards 1979, Powles and'Barans 1980). These fisheries are currently experiencing rapid growth throughout the region. The economic value of these fisheries is difficult to quantify, but the recreational fisheries alone have been conservatively valued in excess of twenty-five million dollars per year in South Carolina and Georgia (D. M. Cupka, pers. comm., S. C. Marine Resources Center, Charleston, S. C., 1981). Because of (1) their ecological and economic importance, (2) the unknown sensitivity of these habitats to environmental perturbation, and (3) a paucity of information which would allow adequate assessment of potential impacts from energy exploration and development, it is imperative that live bottom areas are studied more thoroughly. A recently completed geophysical study by the U. S. Geological Survey (1979) provides information on the distribution of many hard bottom areas, and Henry et al. (1980) provide some insight on important taxa utilizing these habitats. Results of the South Atlantic Hard Bottom Study (Continental Shelf Associates 1979) have also contributed to the biological understanding of these areas. However, information is still inadequate to determine (1) which live bottom areas are important, (2) what relationships exist between these habitats and adjacent non-live bottom habitats, (3) the importance of spatial and temporal patterns exhibited by live bottom organisms, and (4) the necessity (if any) of lease stipulations relative to these areas. This information must be gathered to properly evaluate these biologically important habitats. In response to this need, the Bureau of Land Management (BLM) developed and funded the present biological stu'dy of live bottom habitats entitled the "South Atlantic OCS Area Living Marine Resources Study." For the purpose of this study, the South Atlantic OCS area is that areas bounded by Cape Hatteras on the north and Cape Canaveral on the south and encompassing the continental shelf area within the 19 - 100 m bathymetric zone. PROJECT ORGANIZATION When this contract (#AA550-CT9-27) was initiated, the study was constrained to live bottom areas.on the continental shelf off South Carolina, Georgia,and northern Florida. The contract was awarded to the South Carolina Marine Resources Research Institute (SC MRRI) as prime contractor and the Georgia Coastal Resources Division (GA CRD) as subcontractor. Approximately midway through the study, the project was expanded to include sites off North Carolina. This smaller study was awarded to Duke University Marine Laboratory (DUML) as a subcontractor to the SC MRRI. Due to differences in the scope of work associated with the Duke University effort, the final report has been divided into three volumes. Information presented in this Volume (I) is restricted to efforts and results associated with the original study areas south of Cape Fear. Volume II contains information related to areas north of Cape Fear, and Volume III provides data appendices related to Volumes I and II. 3 Project. Participants: South Carolina Marine Resources Research Institute - The Marine Resources Research Institute of the South Carolina Wildlife and Marine Resources Department isilocated at the South Carolina Marine Resources Center which occupies 30.4 ha (75 acres) adjacent to Charleston Harbor. The Division is broadly charged with the management, development, and proper utilization of the State's coastal resources. This broad mission is discharged through the Division's two major branches, the Off-ice of Conservation, Management and Marketing and the Marine Resources Research Institute. Collectively, these two branches not only manage the state's, marine commercial and recreational fisheries, but also provide the state with a marine research facility capable of technical assistance whenever coastal problems arise. Georgia Coastal Resources Division - Headquartered in Brunswick, the Coastal Resources Division of the Georgia Department of Natural Resources is responsible for the coastal environment of the six coastal Georgia counties and offshore waters to the two hundred mile fisheries conservation limit. Within this area, the Division carries out their responsibilities through diverse functions in three primary areas: fisheries management, coastal protec- tion, and coastal management. The Coastal Fisheries Section's primary responsibilities are to conduct studies necessary for management of Georgia's inshore fisheries, to develop stock assessments, and to draft a management plan for finfish and offshore shellfish. The Coastal Protection Section is charged with maintaining the integrity of the state's coastal ecosystems by protecting them from non- essential degradation. The Coastal Management Section works with local goverrunents and other state agencies to evaluate the availability of natural resources to meet development needs of an expanding coastal economy, By providing technical assistance, legislative participation, and citizen input, the coastal management program is designed to coordinate coastal energy development activities and assist local governments in resource management decisions. Project Management: Management structure of the South Carolina MRRI and Georgia CRD study participants was designed to integrate personnel from both agencies into a unified team (Figure 1.1). Several senior level personnel on the project also have coastal management responsibilities. Thus, pertinent information result- ing from this study is available for their use, even before final publication of the report. The Project Leader was V. G. Burrell, Jr., Director of the South Carolina Marine Resources Research Institute. The Project Coordinator, R. F. Van Dolah, was primarily responsible for managing and monitoring all phases of the contract. He was assisted by J. V. Miglarese in administering this project. Additional key personnel from SC MRRI are identified in Figure 1.1 as responj sible for their respective work elements. The Georgia subcontractor leader was R. J. Reimold, Director of the Coastal Resources Division, who was responsible for Georgia research efforts RLM CONTRACTING OFFICER I PROJECT GEORGIA SUBCONTRACTOR (Burrell) LEADER (Raimold) PROJECT C ORDINATOR GEORGIA COORDINATOR jvon Doloh) (Mohood) ASST.COORDINATOR GA. ASST. C ORDINATOR (Mialoress) Phillips) CRUISE I Iola-- DATA PROCESSING COORDINATION AND LO (Stender) (Gosh) 00 0 X X Z go t) C-# 06 0 0 Z < (a IC 0 r 0 x 0 ow wxZ x x 4 Ma M 0 2.0w 3* vp C 4 0* Mo w -0 010 -4 0 C Z -J SUPPORT7S@TAFF Figure.l.l. General project organization depicting the integrated management structure of South Carolina MRRI and Georgia CRD personnel. GED RGIA (M SSTO G =AA 5 according to contract requirements. R. K. Mahood acted as coordinator for Georgia personnel and was assisted by J. Phillips. Additional key personnel from GACRD are also identified in Figure 1.1 as responsible for their respective work elements. See the Acknowledgements section for a complete listing of all project participants and their areas of responsibility. GENERAL OBJECTIVES AND SCOPE The primary objective of this study was to characterize invertebrate and nektonic communities associated with representative live bottom habitats on the continental shelf off South Carolina, Georgia,and northern Florida. Factors which might influence community structure such as depth, season, latitude, and bottom relief, were considered in the selection of sites and sampling effort. Bathymetric zonation of communities was evaluated by selecting three sites in each of' three different bathymetric zones (19 - 27 m, 28 - 55 m, and 56 - 100 m). The assessment of differences in community structure due to seasonal effects or latitudinal gradients was intended to be a limited effort. Sampling effort was restricted to two seasons (summer, winter) and study areas were confined between 300 and 320N latitude. Characterization of bottom topography and substrate type was also intended to be a limited effort and sophisticated gears, such as; side scan sonar, were not utilized. When possible, study areas within bathymetric zones were selected to provide a range of bottom relief for comparative purposes. A second objective of this study was to evaluate the potential impacts, both detrimental and beneficial, of oil and gas related activities on live bottom communities. Since live bottom areas in the South Atlantic Bight have not yet: been subjected to exploratory activities, this objective is limited to providing hypotheses on potential effects and baseline data on the live bottom communities which might be affected. 6 CHAPTER 2 SAMPLING APPROACH AND METHODS INTRODUCTION Information presented in this chapter is restricted to operations associated with field sampling efforts at the nine southern live bottom study sites. Pertinent data related to all field collections Are listed in Appendices 1 and 2. Laboratory methodologies related to the various sampling activities are presented in subject chapters. LOCATION OF STUDY AREAS The live bottom sites selected for study (Figure 2.1, Table 2.1) were chosen utilizing information from several preceding research programs. These included the South Atlantic Hard Bottom Study and South Atlantic OCS Area Geolog- and Geohazards Studies funded by the Bureau of Land Management; the Marine Resources Monitoring, Assessment and Prediction (MARMAP) program funded by the National Marine Fisheries Service; and unpublished data avail- able to South Carolina MRRI and Georgia CRD scientists. Criteria used in selecting representative sites from the known live bottom areas included bathymetric zone, geographical (latitudinal) location, degree of bottom relief, and areal extent. The three bathymetric zones considered in this study were inner shelf (IS) depths of 19 - 27 m, middle shelf (MS) depths of 28 - 55 m; and outer shelf (OS) depths of 56 - 100 m. Three sites were selected for study in each bathy- metric zone (Figure 2.1). Geographical boundaries for the nine southern sites were initially restricted to the shelf region between 300 and 320N latitude since this area was of greatest interest to industry based on OCS sale 43. Suitable hard bottom areas in the 19 - 27 m bathymetric zone were not found within the original latitudinal boundaries and required extension of the northern boundary to 330N latitude. Within the bathymetric and geographic zones described above, sites were selected to include hard bottom areas with various degrees of rock relief ranging in height from no relief to greater than 2-m relief and ranging in extent of coverage from areas with few outcroppings to areas with a heavy incidence of outcroppings. Additionally, selected sites were restricted to hard bottom areas sufficiently large to ensure that all sampling could be conducted within the designated study area (generally greater than 1 km2). Physical characteristics of each study site are presented in Chapter 4. SAMPLING PERIODS All sites were sampled during winter and summer to obtain information on broad seasonal differences in community structure. Winter samples were collected from 15 January to 26 March 1980, and summer samples were collected 7 @4- so* South Carolina ,-34' V STATIONS DEPTM Z= ISOI-ISO3 19-27m -.-.'-:::.'.-:-'CHARLESTON--. MSOI-MS03 28-55m osol-OS03 56-100m Isole SAVANNAH MSOIO OS010 820 MS02* Georgia OS020 OIS02 BRUNSWI'd MS030 OS030 IS03 JAC ONVILLE-.. i2- 800 Figure 2.1. Location and depth zones of live bottom stations sampled during winter and summer, 1980. 8 Table 2.1. Location of the live bottom stations sampled in winter and summer, 1980. Station Latitude Longitude Lease Block No. IS01 32 029.7' 79042.5' James Island - 446 IS02 31023.6' 80053.1' Brunswick - 596 IS03 30037.1' 81010.6' Jacksonville - 370 MS01 31044.2' 80013.4' Brunswick - 256, 257 MS02 31041.2' 80020.9' Brunswick - 298, 299 MS03 30054.0' 80036.3' Jacksonville - 73 OS01 31032.0' 79044.3' Hoyt Hills - 444, 445 0102 31 008.1' 79055.0' Hoyt Hills - 837 OS03 30025.7' 80012.4' Jacksonville - 565 9 from 4 August to 18 September 1980. Diver assessment of physical habitat characteristics was conducted only once at each sampling site. However, habitat characterization through television transect analysis included both sampling seasons. SAJLING METHODS Research Vessels and Navigation: Remote sampling at the study sites was completed using the 32.6-m R/V Dolphin, operated by the South Carolina Wildlife and Marine Resources Department. Diver sampling was conducted either from the 15.8-m R/V Bagby or the 19.8-m R/V Anna, both of which are operated by the Georgia Department of Natural Resources. All three research vessels were positioned at the study sites using Sitex Model Loran C units. These units provided an approximate repositioning accuracy of + 30 m. To check that the Loran units were functioning properly, disposable pingers (Johnson Lab Inc.) were attached to concrete weights and dropped to the bottom near the center of the study sites. The pingers, operating at 62 KHz, were relocated using a portable hydrophone set (Johnson Lab Inc.) lowered over the side of the research vessel. Hydrographic and Meteorological Methods: Prior to any removal sampling, a Niskin bottle cast was conducted at each study site to obtain hydrographic profiles. Parameters measured at 10-m intervals from surface to bottom were temperature, salinity, dissolved oxygen, and water clarity. Temperature was measured with a certified bucket thermometer for surface samples and with reversing thermometers on Niskin bottles for samples taken at subsurface depths. Salinity samples were collected in 250-ml polyethylene bottles for subsequent analysis in the laboratory. Dissolved oxygen samples were collected in 250-ml polyseal bottles and chemically preserved according to the method of Strickland and Parsons (1972) for analysis in the laboratory. Additional dissolved oxygen measurements were collected at sea from each Niskin bottle using a Yellow Springs Instrument Model 51A oxygen meter and probe. Water clarity profiles were obtained using a Martek Model XMS transmissometer. Measuremen-ts from the transmissometer were noted at 10-M depth intervals and logged on data forms for later analysis. Niskin bottle and transmissometer casts were conducted once per site visit during each season. Light penetration was measured once at each station during both seasonal visits with a Secchi disk. All lowerings were conducted at or near local noon. Weather related observations recorded during sampling included cloud type and percent cover, precipitation, wind speed and direction, barometric pressure9 air temperature, and sea state. These observations were generally recorded for each sampling activity and were helpful in assessing the affects of meteorological conditions on sample quality. Physical Habitat Characterization: Underwater Television Transects - Before removal sampling, all study sites 10 were reconnoitered through television transect surveys. These surveys were designed to provide information on the physical characteristics of each study site as; well as information on the distribution and occurrence of large macrofauna and flora. With respect to physical habitat characterization, television transects were conducted to (1) define boundaries of each study area based on bottom type, (2) evaluate the percentage of different bottom types within study areas, and (3) evaluate the incidence and relief of out- croppings. Transects were conducted using a Hydro Products television system which consisted of a Model TC-125 SDA television camera, a Model C-105 cable assembly and a ship-mounted Model TP-110 camera power supply unit with remote focusing switch. For low light conditions, a Model LT-7 underwater light assembly and a Model LB-250 gas discharge lamp ballast were used with the camera. A Sony Model SLO-340 videotape recorder and a standard 48 cm (19") black and white television monitor were also connected to the Hydro Products system. A microphone connected to this system permitted simultaneous verbal recordJ' 'ngs of Loran C position, time, collection number, and other information on the audio track. The television camera and light assembly were suspended from the research vessel in one of the two frames shown in Figure 2.2, dependent on reconnaissance activity. Generally, the smaller frame (Figure 2.2A) was used for initial reconnaissance activity while the larger frame (Figure 2.2B) was utilized during still camera transects. Transects were completed while the vessel was underway (approximately 1.8 km hr-1), or by drifting when conditions were favorable. In both situa- tions, the camera frame was suspended approximately one metre above bottom. Reconnaissance transects were initiated considerably outside the proposed area for study. During each transect, bottom type was continuously observed on the television monitor, and was recorded every two minutes in data logs along with simultaneous Loran C bearings. Fathometer tracings were recorded throughout the transect. Together with Loran C positioning, this provided an accurate record of the path and depth profile for each transect. The video- tape recorder was activated when an estimate of greater than five percent bottom cover of sessile fauna or rock was detected. Recording continued until six continuous minutes (minimum of 140 m) of sand with less than five percent bottom cover had been observed. Transect paths were selected to minimize overlap and provide adequate assessment of bottom types present, At least three transects were conducted through every study site each season. Analysis of videotapes and fathometer records is described in Chapter 4. Still Camera Transects - Following television reconnaissance, additional characterization of bottom type and fauna was obtained using an Edgerton 35-mm photographic system. This system consisted of a Benthos Model 372 camera equipped with a Model 380-34 data chamber, a Model 383 high intensity flash unit, and a Model 3940 bottom contact switch for remote tripping. The camera system was suspended from the research vessel in a frame (Figure 2.2B) with the camera in a vertical position, A tripper weight, suspended from the contact switch mounted on the frame, activated the camera upon bottom contact and provided a known unit of measure in each photograph for laboratory analysis (Chapter 5). Two series of at least 25 color photographs were taken at each study site: one series taken one metre above bottom and the other series taken three metres A. TV CABLE TO VESSEL IGHT + VANE % TV CAME A TV CABLE TO VE93EL VANE WEIGHT FLASH FOR V UGHT 35mm CAMER TV C'AMERJ 35mtn CAMERA BOTTOM CONTACT SWITCH FOR 35mfn CAMERA TRIPPER WEIGMT FOR 35mrmn CUAMERA Figure 2.2. Schematic diagrams Of two frames (A and B) used for television and still camera transects. 12 above bottom providing photographic records of 0.5-m2 and 3.0-m2 quadrats, respectively. The camera was tripped at constant time intervals along transects across study areas to avoid sampling bias with respect to bottom type and fauna. The television camera was also lowered during still photo transects to taonitor bottom type and ensure that quadrats photographed were within study area boundaries as defined by television transect analysis. Although the photographs obtained from these transects were analyzed for bottom type, the primary intent of this effort was to obtain quantitative information on large macrofauna and flora as well as information on smaller biota riot detected by television transects and not captured by removal sampling gears. Diver Surveys - Physical characterization of the live bottom habitats in the 19 - 27 m and 28 - 55 m bathymetric zones was also accomplished by scuba diver surveys of the study sites. On each survey, the dive team located regions of lowest and highest relief and photographed each area utilizing ambient light and a Nikonos underwater camera loaded with black and white film (TRI-X, ASA 400). Scale was provided by using a 3-m aluminum rod or metre stick marked into 0.33 m and 0.50 m increments and held adjacent to the feature that was photographed. Rock Samples - Attempts were made to collect rocks at all stations for thin section analysis. At stations IS01, IS02, MS02, MS03, and OS01, large rock fragments were obtained in dredge samples described below. Scuba divers collected rocks at stations IS03 and MS02, but no rocks were obtained from stations OS02 and OSO3. All rocks were tagged for identification and brought to the laboratory. Biological Community Characterization: Trawl Sampling - Trawl sampling for fish consisted of standard tows with a 40/54 fly net. This net has the following overall dimensions: 12.2-m (40 ft) headrope, 16.5-m (54 ft) footrope, 12.8-m (42 ft) vertical height. The net is equipped with steel doors and rubber rollers and has the following stretch- mesh dimensions: 20.3 cm in the wings, 10.2 cm in the body, 4.1 cm in the codend,and 0.6 cm in the codend liner. Six replicate tows, three each day and night, were attempted at all low to moderate relief sites. Trawl tows were directed over live bottom areas as defined by underwater television. An attempt was made to standardize trawl samples by towing the net at 100 RPM (about 6.5 km hr-1) for a distance of five Loran C microsecond units. This resulted in an average trawl distance of about one kilometre. Upon retrieval, fishes collected in the trawl were sorted to species, counted, weighed, and measured. Large catches of abundant species were subsampled for length measurements and abundance estimates. Lengths, either fork length or total length when appropriate, were measured to the nearest centimetre. Fishes which could not be identified at sea, as well as represen- tative voucher specimens of all fish species, were preserved in 10% seawater formalin. Subsamples of priority and dominant non-priority fish species wero saved for stomach contents analysis. Fishes utilized for stomach analysis i were individually measured and weighed. Lengths were measured to the nearest millimetre and weight was measured to the nearest gram using an Ohaus Dial-o-Gram balance. Each fish was then dissected and its stomach excised, 13 if not conspicuously empty. Stomachs were individually labeled, wrapped in cheesecloth,and fixed in 10% seawater formalin. Invertebrates captured by the trawl were sorted into major taxa, weighed, and representative specimens preserved for identification in the laboratory. Squid were counted, weighed, and measured (mantle length). 1 Baited Fishing Gear - In addition to trawling, baited fishing gears were deployed in an attempt to collect larger predatory fishes for food habits analysis. Baited fishing gears included Antillean S-traps (122 cm x 122 cm x 61 cm), vertical longlines (10 hooks each), and manual snapper reels. These gears were fished simultaneously in two sets at each station; one set at dawn and one at dusk. Each set consisted of two Antillean fish traps and four vertical longlines fished for about one hour, and three snapper reels fished for about 15 min. Additional rectangular Antillean traps (104 cm x 90 cm x 61 cm) were deployed at some stations during the summer in order to determine the most effective trap design. Fishes captured by baited fishing gears were identified, measured, weighed, and subsampled for stomach analysis in the same manner as described for trawl collections. Juvenile Fish Sled - Sampling for near bottom larval and juvenile fishes which were unavailable to other fishing gears was accomplished with a specially designed epibenthic fish sled. This sled has a mouth opening of 1 m2' a 947-p mesh bag attached to the rear of the sled, and runners which permit the sled to sample 5 cm off the bottom. Although the sled also has a mouth opening mechanism designed to fish only when in contact with the bottom, the door of this mechanism was locked in the open position during most sampling due to sled damage. Two 5-min tows were made per station at night to minimize visual net avoidance. Television and Still Camera Transects - Transect surveys using the television and still camera surveys were utilized to obtain additional information on fish and invertebrates as noted previously. See previous sections in this chapter for details on field methodology and Chapter 5 for laboratory analysis methodology. Diver Swimming Transects - To supplement information obtained through television and still camera transects, diver swimming transects were conducted during both winter and summer seasons at the inner and middle shelf stations. These transects were designed to provide estimates of fish populations and additional characterization of the invertebrate community utilizing still photography. Transects across the dive sites were initiated by locating an area of dense live bottom or ledge and noting a compass reading. From this point, two divers swam side by side, one recording fish species and numbers; the other taking black and white photographs. The photographs were taken in the following manner: At the starting point, four photographs were obtained at 900 angles from each other. The divers then swam 10 kicks along a course dictated by the compass reading, stopped and shot four more photographs in the same manner as before. This procedure was repeated either until the entire roll of film was exposed or until the transect line being followed led the divers off live bottom 14 onto adjacent sand areas. Distances covered by the transects normally ranged between 25 m and 50 m. Random color photographs of representative fauna and flora were also taken along the transect line with a Nikonos 35-mm camera and strobe unit. Jilm obtained from the transects was placed in canisters, labeled, and later pro'cessed into prints or slides for analysis. Rredge Sampling - In addition to the incidental catch of invertebrates in trawl nets, qualitative samples of macroinvertebrates and algae were collected in dredge tows at each station. Dredge tows are especially useful for documenting the presence of large organisms that are relatively rare; smaller organisms capable of escaping other sampling gears; and encrusting, colonial organisms whose presence is only detected when rocks are examined closely in the laboratory. Two replicate dredge tows were made in each study area over live bottom, as determined by television reconnaissance. The length of each tow was standardized to approximately 0.1 km using Loran C positioning. This distance was sufficient to obtain an adequate representation of the biological community for comparisons between stations. With the exception of summer collections at stations OS01 and OS02, all dredge tows were made with a heavy duty rock dredge (Kahlsico No. 215WA420). This dredge has a mouth opening of 60 cm x 37 cm, and a collapsible metal ring bag with a minimum mesh opening of 37 mm x 25 mm. Moderate to high relief at offshore stations resulted in the loss of three rock dredges, in spite of the use of a weak link designed to prevent such loss. This resulted in a reevalu- ation of the requirements for this type of equipment, and led to the replacement of the rock dredge by a heavy duty Cerame-Vivas benthic dredge (mouth opening 90 cm x 37 cm; maximum mesh opening 40 mm x 30 mm). Samples collected in the dredge were sorted on station to remove non- biological material and to subdivide the catch into its major taxonomic components. Dominant components were weighed separately on spring balances to determine their contribution to the total catch biomass. After the samples were weighed, representative specimens of each taxon collected were placed.in labeled containers, preserved in 10% buffered seawater formalin, and brought to the laboratory for identification. Rocks collected in the dredge were also saved. Suction Sampling - Quantitative suction samples of smaller benthic invertebrates, not adequately sampled by previously described gears, were obtained at inner and middle shelf sites by scuba divers. Using Loran C coordinates of known hard bottom, divers obtained five replicate samples at each station from a suitable area chosen to avoid large patches of sand commonly found at the sites. A disc with five equally spaced radial marks was dropped to the bottom and a 3-m line, fastened to the center of the disc, was then used to place five quadrat boxes (0.1 m2, 10-cm walls, open on both ends) equidistant from the disc. Exact positioning of the quadrat boxes was 'ished by randomly selecting one of nine possible quadrat areas from a accompl larger grid frame attached to the 3-m line. Fauna within the quadrat was sampled by scraping the area while simultaneously sucking with an airlift device similar to that described by Chess (1979). All suction samples were collected in 1.0-mm mesh bags and brought to the surface for preservation. On deck, each sample was narcotized with magnesium chloride and preserved in 15 10% seawater formalin. During the winter sampling period, one sample was lost from two stations (MS01, MS02) resulting in only four replicate samples for those stations. Grab Sampling - At the outer shelf stations (OS01, OS02, and OS03) where water depth precluded the use of the suction device operated by divers, qualtitative 0.1 m2-samples were collected with a modified Smith-McIntyre grab (Kahlsico No. 214WA250). This sampler is a spring loaded grab that is triggered upon contact with the bottom, and has been found to be the most successful of its type for use in open sea conditions on compacted sediments or hard surfaces. The grab was lowered over live bottom within the study area, as determined by previous television transect records and five replicate samples were obtained. In most instances, numerous attempts were necessary to obtain five adequate samples. This was usually due to failure of the tripping mechanism, or to improper closure of the grab when the jaws were held open by rock or shell fragments. After retrieval, each sample was placed into a one millimetre sieve and washed to remove the finer sediment. Excess non-biological material was then removed, and the remaining contents were rinsed into labelled containers and preserved in 10% buffered seawater formalin. 16 CHAPTER 3 HYDROGRAPHY AND WEATHER OBSERVATIONS INTRODUCTION The hydrographical and meteorological portions of this study were complementary to the biological sampling, with the hydrographic sampling limited in scope. The primary intent of hydrographic sampling was to provide environmental data at the nine live bottom stations when biological samples were obtained, not to delineate conditions throughout the entire South Atlantic Bight. Several references are available which contain detailed and comprehen- sive physical and chemical data for the South Atlantic Bight. Bumpus (1955) described circulation along the continental shelf, utilizing drift bottles. Rao et al. (1971) utilized satellite infrared imagery to locate Gulf Stream meanders and eddies. Mathews and Pashuk (1977) provided large amounts of chemical and physical data with some general current descriptions * Atkinson (1978) published the results of four cruises in the Georgia Bight with abundant physical and chemical data, including limited drift bottle results. Finally, extensive physical and chemical data are available through the South Atlantic OCS Physical Oceanography Study (Science Applications, Inc. 1981). The South Atlantic OCS Study provides good descriptions of large scale current patterns. Studies off the North Carolina coast that provide similar information on currents as well as physical and chemical parameters include Wells and Gray (1960), Gray and Cerame-Vivas (1963), Stefansson et al. (1971), Blanton (1971) and Schumacher and Korgen (1976). LABORATORY METHODS Salinity and dissolved oxygen (DO) samples were returned to the MRRI chemistry laboratory for analysis. Salinity samples were analyzed on a Beckman RS-711 induction salinometer. DO samples were treated with H2SO4 and titrated with Na2S203 in the standard Winkler-Carpenter iodometric method (Strickland and Parsons 1972). Salinity, dissolved oxygen, transmissometry, and temperature data were tabulated for further analysis and interpretation. RESULTS I Water Cemperature: In general, the winter water temperature followed regular trends, i.e., colder water inshore of the Gulf Stream and limited stratification except at- offshore stations (Figure 3.1, Appendix 3). Inshore stations were distinctl? colder than those offshore, e.g. 12.280C (surface) at IS02 vs. 19.950C (surface) at OSO,2, and 14.070C (surface) at IS03 vs. 21.540C (surface) at OS03 (Figure 3.1). Weak stratification was observed at several stations, with the strongest 17 0C 12 14 16 18 20 Z2 1 214216 1 218- 0- TEMPERATURE 10- 20- ISOI S U M M E R 301 WINTER 0- 10- CL 20- IS02 12 14 16 is 20 22 24 26 28 W 0- 301 10- 20- 10- IS03 30- 3@ 40- OSOI o- 10- 0- 20- IVISO 1 10- 30-j 20- 0- 1-1 1 t I I I I Iift 30- E 10- 40- OS02 20- MSOz 50- CL W 30J 0- 1 t I I -I I I I 0- 10- 20- 20- 30- IVISO 3 40- OS03 9 (0--,,@Oso I Z ZOS 0?- @@?SO3 Figure 3.1. Vertical profiles of water temperature (00 at live bottom stations during winter and summer, 1980. 18 vertical temperature gradient present at OS01 (0.080C m-1 ). At two stations, surface! waters were colder than subsurface waters at 10 m. Temperatures at IS03 On the surface and at 10 m were 14.070C and 14.460C, respectively, while at OSO-3 water4temperature was 21.540C at the surface and 21.630C at 10 m. Summer whter temperatures indicated highly stratified conditions with well defined thermoclines at most stations, e.g., vertical temperature gradients were 0.310C m-l at IS01, 0.230C m-l at OS01, and 0.300C m-l at MS03. Little stratification was evident at IS02, where temperatures ranged from 28.490C on the surface to 28.400C at 14 m (Figure 3.1). Differences in summer inshore and offshore temperatures were relatively small, especially when compared to winter temperature variations. All surface water temperatures were in the range of about 27.80 - 29.20C. Salinity: Winter salinities were > 36.0 O/oo, regardless of depth, at all stations except IS02, ISO3,and MS03 (Figures 3.2 - 3.4, Appendix 4). The lower salinity water at these three stations may be a reflection of runoff from the Savannah, Altamaha, and other Georgia rivers (see Figure 3.2). Most stations had very low vertical salinity gradients, with typical values being < 0.006 O/oo m 1. The maximum salinity at most stations occurred below the surface (Figures 3.2 - 3.4). Summer salinities were generally high with no values < 35.0 0 o Vertical salinity gradients were relatively low, e.g., 0.047 O/oo m- (OS03), but somewhat greater than winter values. As in the case of winter salinities, maxima at most stations occurred below the surface (Figures 3.2 - 3.4). Dissolved Oxygen: This contract required that all DO concentrations measured by the oxygen meter -at sea be confirmed by chemical laboratory analyses. However, due to the time lag between the collection and analysis of DO samples, the titration data proved unreliable. Consequently, DO measurements presented in this chapter represent values obtained with the DO meter. Winter dissolved oxygen concentrations were all > 4.7 ml 1-1, with the majority being > 5.0 ml 1-1 (Figures 3.2 - 3.4, Appendix 5). Only stations OS02 and OS03 had dissolved oxygen concentrations < 5.0 ml 1-1 (> 40 m depth) (Figure 3.4). The maximum concentration of 6.73 ml 1-1 occurred-at IS02 (surface), which had the coldest water temperature and next to the lowest salinity of any of the winter stations (Figure 3.2). Oxygen maxima occurred at the surface at five stations during the winter cruise, possibly due to wind mixing. Summer dissolved oxygen concentrations were somewhat lower than winter values due to higher water temperatures, biological activity,and stratification, i.e., little wind mixing. Most concentrations were > 4.0 ml 1-1, with only four samples being < 4.0 ml 1-1 at or near the bottom (Figures 3.2 - 3.4). Few concentrations exceeded 5.0 ml 1-1, and these were subsurface measurements in each instance. Oxygen saturation ranged from 89% - 112% during the winter and 66% - 106% during the summer. Generally, percent saturation was higher on the surface than near the bottom. During the summer cruise the surface saturation was up 19 WINTER ISM SUMMER SALINITY SALINITY 33 34 U 36 37 33 34 35 36 37 0. 0- 10- 10- W n 3.0 410 5.0 6.0 7.0 --iO 4.0 5.0 6.0 7'0 OXYGEN OXYGEN SALI N ITY IS02 SALINITY 33 34 35 36 37 33 34 35 36 37 0- 0- E 10- 10- W 2 20 0 4*0 5'0 6.0 7.0 3.0 4.0 5.0 6.0 7.0 OXYGEN OXYGEN SALINITY IS03 SALINITY 33 34 35 36 38 33 34 3P 36 37 0. 0- r 10- 10- CL W 201 20 3.0 4.0 5.0 6!0 ?'0 3.0 4.0 5.0 6. 0 i.0 OXYGEN 0----o SALINITY OXYGEN 0-0 OXYGEN Figure 3.2. Vertical profiles of salinity (0/oo) and dissolved oxygen (ml 1- at inner shelf stations during winter and suffner, 1980. 20 WINTER SUMMER MS01 2 SALINITY SALINITY 33 34 35 36 37 33 34 35 36 37 0-- 0- lo- lo. W 2 .0 30- ----,,30 3.0 410 5.0 6.0 7.0 3'0 410 5.0 6.0 -'r-o OXYGEN MS02 OXYGEN SALINITY SALINITY 33 34 35 36 37 33 34 35 36 37 0. 0. E lo- lo- W 20- 3 30- 3.0 4.0 5.0 6.0 7.0 3.0 4.0 5.0 6.0, 7.0 OXYGEN MS03 OXYGEN SALINITY* SALI NITY 33 34 35 36 37 33 34 35 36 37 0- 0- J 10- 10- E X 20- 20- CL W 30- 30- 3.0 4.0 50 6,0 7. 0 OXY`GEN 40 0 *SALINITY 3.0 4.0 5.0 6.0 7.0 OXYGEN Figure 3.3. Vertical profiles of salinity (0/oo) and dissolved oxygen (ml I mm st at middle shelf ations during winter and su er, 1980. 21 WINTER 0sol SUMMER SALINITY SALINITY 33 44 35 36 IIS 33 34 33 36 37 0- 0- 30- 30- IL 0 so- So- 4- go- &0 4 5!0 G!o ;A &o @o *'o 6!o F,o OXYGEN ()SOZ OXYGtN SALINITY SALINITY 33 14 34 U 33 34 35 36 ST 0. 10. to- to- 7. 30- 40- 40- 3@0 16.0 5.0 6.0 -P.@'-3'0 4,0 @0 4'o T-0 OXYGEN OS03 OXYGEN SALINITY SALINITY 33 34 35 34 V 33 34 311 34 37 -. - 10- .I T 10. 10- 916 W So- o 40- 40- 0 070 *!o swo @o 7. &0 4.0 51. to 7.0 OXYGEN OXYGEN 0---* SALINITY 9--* OXYGEN Figure 3.4. Vertical profiles of salinity (0/oo) and dissolved oxygen (ml at outer shelf stations during winter and summer, 1980. 22 to 35% higher than bottom saturation, primarily at the outer shelf stations. The winter surface saturation was not always greater than bottom saturation and was-, not more than 22% higher in any case. Both summer and winter oxygen saturations illustrate stratified versus well-mixed conditions. There were, however, no obvious relationships between percent saturation and station location. Representative values are reported in Appendix 5. Light Transmission: Light transmission was generally less variable with depth during winter than summer; however, the overall percent transmission was not significantly different for the two seasons, despite some seasonal variations at individual stations (Figure 3.5). Light transmission was greatest below the surface at six winter stations and five summer stations (Figure 3.5, Appendix 6). The maximum was always found either at the surface or at the greatest sampling depth. The minimum, on the other hand, was at intermediate depths at three winter stations and four summer stations. Finally, the time of day appeared to have little effect on percent transmj@ 'ssion. Daytime measurements were comparable for both the winter and summer cruises. Light Penetration: Despite the inaccuracy of Secchi disc measurements, some general trends were detected. Light penetration was greater during summer than during winter, due perhaps to calmer, more highly stratified conditions prevalent during the warm summer months (Appendix 6). Light penetration did not reflect any patterns with respect to depth during either season (Appendix 6). Meteorological Observations: The results of meteorological observations are presented in Appendices 1 and 2. Predictably, air temperatures were lower and wind velocities were higher in winter than in summer. However, the short term effects of variations in air temperature, wind velocity and barometric pressure were too subtle to detect in our water column data. DISCUSSION Overall, the hydrographic data generated by this study indicate conditions typical of the South Atlantic Bight. Nearshore waters had larger ranges of temperature and salinity than offshore waters, corresponding to seasonal or long term meteorological influences. The offshore stations (OSOI, OSO2, and OS03) had consistently warmer surface waters,(up to 81C in winter) than inshore stations (IS01, ISO2, and IS03) (Appendices 3 and 4). While salinity was generally > 35.00 O/oo, the winter salinities at IS02, ISO3, and MS03 were j as low as 33.29 O/oo, probably due to river runoff. Low salinities in the 1. same area have also been observed by Maihews and Pashuk (1977), Atkinson (1978), and Science Applications, Inc. (1981). 23 PERCENT 30 4 10 so sp -r1O 810 9P Igo LIGHT 0- 10- TRANSMISSION 20- ISOI o --- o SUMMER 3 *---o WINTER lo- PERCENT 40 50 60 70 90 too ISO?- 0- -@O W to- 10- 20- 30- IS03 40- 5 -OSOI 60 0- 10- ? MS01 10- 301 20- 0-- 30- E 10- MS02 40- OS02 50-J (L 20- o- W 0- 10- 10- 20- 20- 30- 30- MS03 40- OS03 40- 50--@ Figure 3.5. Vertical profiles of light transmission at live bottom stations during winter and summer, 1980. 2 24 Dissolved oxygen concentrations were, for the most part, near saturation, with some stations having supersaturated concentrations (Appendix 5). The DO concentrations are indicative of conditions commonly found along the shelf, i.e., highly oxygenated waters, unstressed by a high biochemical oxygen demand (BOD) associated with decaying organic matter or some chemical pollutants. Mathews and Pashuk (1977) and Atkinson (1978) recorded DO concentrations in the same range as those reported in this study for the same geographical area. It is riot unusual for DO concentrations at the surface or in shallow waters to be affected by localized meteorological influences, such as high winds with concommitant wave action resulting in increased wind mixing of oxygen * Despite the inherent difficulties in interpreting the transmissometry data, some general relationships are evident. Since the transmissometer has a built-in light source, it measures light transmission through a given path length and not light penetration from the surface. Hence, percent transmission should be independent of depth and time of day, but not of solids, phyto- plankters, and other light scattering constituents. Our data, in fact, support these premises since there is no apparent relationship between depth or time of day and percent transmission. Transmission may be reduced by the suspension of bottom sediments due to wind induced turbulence, but this is not supported by our data. IMPACT/ENHANCEMENT Due to the limited scope of this study, it is not possible to accurately predict: the impacts-of drilling for oil or gas relative to hydrography. Some possible effects on the parameters measured, however, include reduced light transmJ' _ssion and DO concentrations due to the suspension of anoxic bottom sediments. Presumably, these effects would be localized or short term due to the rel 'atively strong currents along the coast (Bumpus 1955, Mathews and Pashuk 1977). Additional impacts are difficult to predict, based on our present data base. CONCLUSIONS - Overall, the values of hydrographic parameters measured at the live bottom sites during this study were typical of the South Atlantic Bight. - Salinities were uniformly high (> 35. 00 O/oo) at all depths and at all stations except for IS02, IS03, and MS03, which were probably influenced by increased river runoff during winter. Temperatures varied predictably, with inner shelf waters exhibiting a wider range than outer shelf waters. A low of 12.280C was recorded at IS02 during January 1980, while a high of 29.220C was recorded during August 1980 at OSO3. Dissolved oxygen concentrations were generally high at all station and dept'hs, ranging from 3.63 ml 1-1 to 6.73 ml 1 1 and 66% to 112% saturation. Light: transmission ranged from 38% to 90% transmission. Secchi disc readings varied from 6.0 m to 31.0 m. 25 CHAPTER 4 PHYSICAL HABITAT CHARACTERIZATION INTRODUCTION Recent oil lease activity in the Georgia Bight has been accompanied by extensive topographical and geological surveys. A variety of geophysical equipment, including precision depth recorders, side scan sonar devices, and subbottom profilers have been used to conduct these investigations (U. S. Geological Survey 1979). These surveys have provided information on the occurrence of potential geological hazards associated with petroleum develop- ment, textural characteristics of the bottom sediments, and topographic features of selected areas on the continental shelf. They have also led to the identification of shallow subsurface reflectors (hard bottom) which may or may not: be indicative of live bottom. Because hard grounds such as these are often covered by a layer of sand which may prevent accumulation of sessile epifauna, it is often necessary to employ means of detecting live bottom other than geophysical surveys such as those previously described. A recent report to the Bureau of Land Management (Continental Shelf Associates 1979) has demonstrated the importance of using underwater television to make visual observations of geophysically detected hard bottom. This gear is useful for delineating the discontinuous nature of emergent hard bottom areas and characterizing the types of biological assemblages associated with them. Underwater television also has been used along with side scan sonar to classify the morphology of reefs and hard grounds and to describe the distribution of hard bottom areas in a survey of the Georgia Bight (Henry and Giles 1979, Henry et al. 1980). In addition, this gear has been used to estimate the amount of reef habitat on the continental shelf of the South Atlantic and Gulf of Mexico (Parker et al. in preparation). Although the primary focus of the present study was on the living resources Of live bottom habitats, it was also necessary to describe the physical characteristics of the study sites. These descriptions were based on informa- tion obtained through television and still camera transects, fathometer tracings, diver observations, and analysis of rock samples. Underwater tele- vision transects were intended to define approximate boundaries of the selected areas, location and extent of outcroppings, and together with still photograph analysis, to provide an estimate of percent cover of sand versus live bottom within the boundaries of the study area. The fathometer was utilized to define the depth range within the study area, and diver observations and rock samples were utilized to assess the degree of habitat complexity and the geological nature of outcroppings. METHOD'S OF LABORATORY ANALYSIS Television Transects: Television transect videotapes were reviewed in the laboratory to eliminate those which were unsuitable for analysis due to poor visibility. Duration of 26 tape segments to be analyzed was also noted. Analysis of tape segments commenced either at the beginning of the videotape recording for a particular transect or at the Loran C position (recorded on tape) closest to the first evidence of live bottom (> 5% bottom cover of rock or sessile fauna). Analysis ended at the Loran C position immediately following last evidence of live bottom (< 5% bottom covjr) or when the videotape recorder was turned off. Absence of live bottom for-three consecutive Loran C readings (6 min, minimum of 140 m) was the criterion used for last evidence of live bottom. However, shorter gaps of sand between patches of live bottom were included in the analysis when they occurred. Attempts were made to select three transects from each study area to provide a total of 60 min of analysis per study area per season. When transects were longer than 20 min, only 20 min were selected for analysis. If transects were shorter than 20 min, more than three transects were analyzed. For most stations, three or more transects were randomly selected from a larger number available for analysis. Bottom type at each study area was assessed by noting presence or absence of live/hard bottom during 10-sec intervals along the entire length of each transect. Since speed was usually constant during a transect, these time inter- vals divided each transect into numerous, short, and approximately equal distance intervals. A mean proportional estimate of bottom type was obtained for every study area by determining the number of intervals with different bottom types noted on the transects. The three categories of bottom type that were analyzed included thin sand with hard bottom fauna present, rock outcroppings, and sand with no evidence of hard bottom fauna present. During assessment of bottom type, only the lower middle third of the television monitor was viewed. This restriction reduced variability caused by poor visibility and fluctuations in the distance of the camera above bottom. Fathometer Readings: Fathometer tracings obtained during television transects were examined in the laboratory to determine depth extremes within study areas. Minimum and maximum depths were measured on each tracing and tabulated. Still Camera Transects: Ektachrome film (ASA 160) exposed during one- and three-metre photographic transects was processed, mounted in slide frames and labelled with collection numbers, slide number, date, and time of exposure. All slides were reviewed to determine suitability for analysis., Slides eliminated from further analysis included: (1) photographs taken prior to the first or following the last evidence of live bottom, (2) photographs in which the bottom or the tripper weight was not visible, and (3) photographs taken unintentionally by inadvertent bouncing of the tripper weight. All remaining photographs collected at a study area were sequentially numbered, and 25 slides from each transect series (1 m and 3 m) were randomly selected for analysis. During quadrat analysis of macrofauna (described in Chapter 5) the bottom type observed in each slide was noted and tabulated. P Rock Analysis: Rocks were obtained from all study areas except OS02 and OS03, where repeated dredge tows failed to retrieve rocks of sufficient size for analysis. 27 Rocks collected by divers and dredge tows were brought to the laboratory and subjectively examined to determine degree of rugosity and cribriformity. Sessile fauna having calcareous components were also identified because they contributed heavilv to ro k surface texture. Rocks were then broken apart to obtain non- eroded pieces for thin section analysis. All thin sections were stained to differentiate calcite and dolomite. Constituents forming each rock specimen were identified through binocular analyses of thin sections. The proportional contribution of each rock constituent was estimated using standardized visual estimate charts (Terry and Chilingar 1955). RESULTS Description of the Study Sites: Observations recorded during videotape interpretation, along with notes made by scuba divers at the inner and middle shelf stations, are summarized in the following site descriptions. The terminology used in describing various degrees of rock relief conforms to the categories defined by Henry and Giles (1979): (1) low relief is less than 0.5 m, (2) moderate relief ranges from 0.5 mto 2m, and (3) high relief (shelf edge) is greater than 2 m. Maps that accompany these descriptions were compiled using Loran C position plots for television transects and logs maintained during videotaping and subsequent videotape analysis. The boundary shown on each map was determined by connect- ing the points which designate the approximate location of the first or last evidence of live bottom on the most peripheral television transects. Thus, all or only a portion of a given transect may fall within the boundary of a study area as defined above. The areal extent of each study site was approximated by geometrically determining the area within the boundary, using the scale which accompanies each map. Inner Shelf Stations - Station ISOI was an extensive 4.5-km area situated approximately 31 km southeast of Charleston, South Carolina in James Island Lease Block 446. Fathometer recordings made during television transects indicated that water depths at this location ranged from 16.5 m to 18.3 m (Table 4.1). This station was characterized by a moderately heavy growth of sessile invertebrates distributed somewhat uniformly over a broad expanse of hardpan overlaid by a thin layer of sand (4 - 8 cm). Bottom topography was rather smooth, with little relief and only occasional cracks or depressions in the substratum. Other than a few small ledges (< 0.5 m), no significant rock outcroppings were observed on videotapes from this station (Figure 4.1). Station IS02 was a smaller area of dense live bottom, measuring approxi- mately 1.4 km2 in size. This study site was only one reef patch within the much larger Gray's Reef area described by Hunt (1974). This station was located approximately 32 km due east of Sapelo Island, Georgia, in Brunswick Lease Block 596, where water depths ranged from 16.5 m to 21.5 m (Table 4.1). Bottom topography consisted of numerous rock ledges (Figure 4.2) up to one metre in height, which were covered with a heavy growth of encrusting and sessile invertebrates. The ledges were comparable to those described by Hunt (1974) and were distributed throughout areas of sand which supported thick epifaunal growth, particularly adjacent to the ledges. The density of growth - nrowth decreased with distance from the ledges, and graded into the sparser g @ypical of hardpan are -as. Also observed-were-occa -sion-al patches- -6-f-pdr-6--sand that supported no apparent growth., presumably because acciiiulation o d was t&@__thick to allow attachment of -e.pif-auna to su&s_u_r@_i-ioc-k_.-- 28 Table 4.1. Depths recorded by fathometer during television transects. Mean values represent the average of minimum (or maximum) depths from all transects conducted at each station during both sampling periods. Mean Mean No. of Minimum Maximum Depth Station Transects Depth (m) Depth (m) Extremes W IS01 5 17.1 17.5 16.5-18.3 IS02 5 17.0 19.6 16.5-21.5 IS03 4 20.6 21.5 20.1-22.0 Msol 9 30.9 33.0 24.7-34.8 MS02 6 26.2 28.6 23.3-29.3 MS03 2 33.8 36.8 33.8-37.5 Osol 3 59.4 66.2 58.5-66.8 OS02 8 48.9 54.3 46.6-57.6 OS03 2 54.0 61.5 54.0-63.1 29 60542 60522 45418 45418 IS01 0 400m +-32-29.7'N 79042.5'W 4,5404 1 45404 60542 60522 Figure 4.1. Location of television transects at Station IS01. Dashed line represents boundary of study area, heavy segments represent portions of transects used in analysis, and dot (southeast corner of study area) shows location of rock outcropping on analyzed portions. Corner coordinates are Loran C units. 30 61531 61521 45467- 45467 IS02 ItI 0 200M L---L---i +-31-23.6-N 80*53.1'W 45458+--- _7 45458 1 61531 61521 Figure 4.2. Location of television transects at Station IS02. Dashed line represents boundary of study area, heavy segments represent portions of transects used in analysis, and dots show locations of rock outcroppings on analyzed portions. Corner coordinates are Loran C units. 31 Station IS03 was located 30 km east of Amelia Island, Florida in Jackson- ville 'Lease Block 370. Water depths at this site varied from 20.1 m to 22.0 m (Table 4.1), and the areal extent (1.6 km2) was roughly equivalent to that of IS02. IS03 was an area of patchy live bottom with low relief. The topography of the bottor@ was quite similar to IS02, although ledges were less frequent (Figure 4.3) and lower than those at IS02. Epifaunal growth, particularly sponges and octocorals, was sometimes heavy and often occurred in areas of hard bottom covered by sand as well as on exposed rock. A larger amount of bare sand was observed at this site than at other inner shelf stations. Middle Shelf Stations - Station MS01 was a small area (0.6 km2) located 67 km east-southeast of Savannah, Georgia, on the border of Brunswick Lease Blocks 256 and 257. Water depths at this station ranged from 24.7 m to 34.8 m (Table 4.1). Extensive areas of rock outcroppings, as well as hardpan covered by coarse sand, were observed at this site (Figure 4.4). The outcroppings were of moderate relief, approximately one-half to one metre in height. Bottom topography was similar to IS02, with ledges appearing as linear features that occasionally intersected one another, but which were otherwise separated by areas of sand of varying thickness. Much of the sandy area had no epifaunal growth. Conversely, areas of moderate relief were typically covered by a very heavy growth, particularly sponges and octocorals, while epifaunal growth on low relief hardpan was usually sparse. Station 11S02 was situated 63 km southeast of Savannah, Georgia, and 13 km southwest of MS01. In addition to their proximity, MS01 and MS02 were roughly equivalent in size, being about 0.6 km2. MS02 was located in Brunswick Lease Block 298 and 299, in water depths ranging from 23.3 m to 29.3 m (Table 4.1). Despite their proximity, MS01 and MS02 were dissimilar in that MS02 was characterized by having few distinct ledges (Figure 4.5). It did, however, possess some patchy areas of outcroppings with low, broken relief, where cracks and crevices were numerous. Large expanses of sand-covered hardpan lay between the outcroppings and supported moderate growths of sponges, although most of the biota was concentrated on the outcroppings. A considerable amount of bare sand was interspersed throughout the area. Station MS03 encompassed an area of 4.7 km2 and was considerably larger than the other middle shelf stations. It was located 81 km east-southeast of Brunswick, Georgia, in Jacksonville Lease Block 73. Water depths ranged from 33.8 m to 37.5 m (Table 4.1). Analysis of television transects indicated that rocky outcrops were sparse at this station and very patchy within areas of bare sand. A few ledges of low relief were observed (Figure 4.6), some with heavy growth but others were rather bare. Diver observations, however, revealed a bottom topography at MS03 more similar to IS02, with ledges of moderate relief and a flat hardpan plateau. These observations of moderate relief not recorded on videotape indicate that the television transects did not completely census this extensive area. Outer Shelf Stations - Station OS01 was the smallest study area (0.4 km2) and was located on the border between Hoyt Hills Lease Blocks 444 and 445, ' approximately 120 km east-southeast of Savannah, Georgia. Water depths ranged from 58.5 m to 66.8 m (Table 4.1). This site contained a moderate amount of flat exposed rock with sparse epifaunal growth. Relief was generally very low, 32 61899 61889 1 45293- 45293 IS03 0 200M +-30037.1'N 80010-6,W 45280- 1 45280 61899 61889 Figure 4.3. Location of television transects at Station IS03. Dashed line represents boundary of study area, heavy segments represent portions of transects used in analysis, and dots show locations of rock outcroppings on analyzed portions. Corner coordinates are Loran C units. 33 61075 61065 45352- 45352 MSOI 0 200m L---4 ---j - +-31*44.2'N 80013.4'W 45342- 45342 61075 61065 Figure 4.4. Location of tele vision transects at Station MS01. Dashed line represents boundary of study area, heavy segments represent portions of transects used in analysis, and dots show locations of rock outcroppings on anal*yzed portions. Corner coordinates are Loran C units. 34 61155 61145 45375- 45375 M S02 0 200M -31-41.2- N 80*?-0.9'W 45365 45365 61155 61145 Figure 4.5. Location of television transects at Station MS02. Dashed line represents boundary of study area, heavy segments represent portions of transects used in analysis, and-dots show locations of rock outcroppings on analyzed portions. Corner coordinates are Loran C units. 35 61539 61 19 45192- -45192 MS03 0 400m % -30*54.0'N % 80*36.3'W % 45176 45176 L 61539 61519 Figure 4.6. Location of television transects at Station MS03. Dashed line represents boundary of study area, heavy segments represent portions of transects used in analysis, and dots show locations of rock outcroppings on analyzed portions. Corner coordinates are Loran C units. 36 with only a few ledges of notable height observed (Figure 4.7). Occasional patches of thin sand contained some epifauna, but this growth was light compared with inner shelf stations. 2 Station OS02 was a narrow, elongated area of 1.3 km , located in Hoyt Hills Lease Block 837, roughly 141 km east of Brunswick, Georgia. Water depths at jbis site ranged from 46.6 m to 57.6 m (Table 4.1). Television reconnais- sance and videotape transects revealed a narrow, concentrated band of ledges with a north-south orientation (Figure 4.8). These ledges were of moderate relief, and large rectangular rocks up to a metre or more in length were common. These rocks supported a light growth of sponges and octocorals, and were interspersed among patches of barren sand. Station OS03 was similar to OS02 in bottom topography. It was a narrow area of extensive rocky outcroppings which covered 3.3 km2 (Figure 4.9) in Jacksonville Lease Block 565, approximately 115 km east of Jacksonville, Florida. Water depths ranged from 54.0 m to 63.1 m (Table 4.1). Relief at OS03 was moderate to high (up to 2 m), and many large rectangular blocks like those at OS02 supported moderate growths of sponges. Some rocks were covered by thin sand, but little bare sand was observed. Rock rubble was noted at the foot of some of the larger rock prominences. Substratum Analysis: Estimates of the proportion of different bottom types,as determined from videotape analysis, varied considerably among stations and among replicate transects within stations (Figure 4.10). Total estimates of live bottom occurrence for each station included sessile epifauna observed on both rock outcroppings (shaded portions of histograms) and hardpan with a layer of sand (unshaded portions of histograms). Values of the histograms that were less than 100% indicated the presence of sandy areas interspersed among patches of live bottom. Thus, although the percent frequency of live bottom on videotaped transects was generally quite high, the occurrence of actual rock outcroppings was less frequent (Figure 4.10). Emergent rock was uncommon at all inshore stations except IS02 and was also quite infrequent at middle shelf stations except at MS01. Rock outcroppings were uncommon at OS01 as well, but were more frequently encountered at OS02 and OS03 than at all other stations. The relative proportion of emergent rock (Figure 4.10) agreed with the observations made by scuba divers and with the frequency of ledges shown on individual station maps (Figures 4.1 through 4.9). Live bottom estimates were lowest at MS03, where the mean percent frequency of occurrence was only 45% (Figure 4.10). Estimates for all other stations were considerably higher, with mean values greater than 60%. Heterogeneity of variances at many stations precluded the use of analysis of variance to test for significant differences; however, the non-parametric Kruskal-Wallis test (Sokal and Rohlf 1969) indicated a significant difference in the percentage of live bottom among study areas (P < 0.001). Although unequal sample sizes prevented statistical verification, it seems likely that this difference was due to the extremely low values at MS03 (Figure 4.10). Estimates of the proportion of various bottom types, as determined from still photographs, also showed high variability among stations (Figure 4.10), probably due to the small quadrat size and patchy nature of the bottom. Nevertheless, estimates from both 1-m and 3-m elevations generally agreed with 37 45125 45139 60907- 60907 OSOI 40 Om -0'-31-32.0-N 79044.3'W 60883 60883 45125 45139 1 Figure @4.7. Location of television transects at Station OSO1. Dashed line represents boundary of study area, heavy segments represent portions of transects used in analysis, and dots show locations-@ of rock outcroppings on analyzed portions. Corner coordinates are Loran C units. 38 61130 61110 45053- 45055 OS02 ell Ir 0 400m N 79*55.0'W 45037 45037 61130 61110 Figure 4.8. Location of television transects at Station OSO2. Dashed line represents boundary of study area, heavy segments represents portions of transects used in analysis, and dots show locations of rock outcroppings on analyzed portions. Corner coordinates are Loran C units. 39 61477 61457 44869- -44869 N OS03 400m --j - ---------------- ------ +-30*25.7'N - Boo I 2.4'W 4485 T-- r-- 44850 F; 147 7 61457 Figure 4.9. Location of television transects at Station OSO3. Dashed line represents boundary of study area, heavy segments represent portions of transects used in analysis, and dots show locations of rock outcroppings on analyzed portions. Corner coordinates are Loran C units. Television Transects(with replicate At) * Photography Transects(Im above bottom) * Photography Transects(3m above bottom) 100- 80- 2 0 41 0 0 60- 00 0 w > 0 40- 0-0- 2o- 01 1, ..... ...... N 0) 6 N K) 0j K) 0 0 0 0 0 0 U) U) U) 0 U) U) U) Cn (n H H 2 2 2 0 0 0 STATIONS Figure 4.10. Mean percent frequency of live bottom from videotape analysis of the study sites. Heavy vertical lines represent standard error of the mean and thin vertical lines indicate the range. Shaded portions of the histograms represent the mean percent frequency of rock outcroppings. Circles represent the percent frequency of live bottom estimates from still photographs. 41 those made from television transects, often falling within the range of values from videotape analysis at a given station. Analysis of still photographs indicated that station MS03 had the lowest frequency (25%) of live bottom, although no trends were apparent among the other stations. At stations where photographs were taken at both 1 m and 3 m above bottom, the 1-m photographs usually yielded higher estimates of percent live bottom than did the 3-m photographs. It is likely that this difference is a result of better visual resolution of organisms in the closer photographs. Rock Analyses: Thin sections from rock samples contained sandy limestones, with the exception of OS01, which was a quartz sandstone cemented by cryptocrystalline micrete (Table 4.2). These limestones are sandy (Quartzose) biomicrites, according to the classification of Folk (1959). Notable quantities of the phosphate mineral collophane and phosphorite sand grains were found at IS01 and MS03, respectively (Table 4.2). The collophane of station IS01 was a secondary replacement of the original crypto- crystalline micrite cement. In specimens from MS01 and MS02, this original cryptocrystalline micrite cement has been partially recrystallized to coarser crystalline sparry calcite. Thin sections were not made on rock specimens from IS02, since photographic details were available for rocks collected by Hunt (1974) in the area of Gray's Reef. All rocks described by Hunt were similar to one another in composition. They were unlike those described in this study, however, in that the sandy biomicrite had been moderately to strongly dolomitized. Table 4.2 includes a summary of the characteristic features of Hunt's specimens. With the exception of IS01, all specimens contained considerable quanti- ties of fossil fragments, ranging from 20% at MS03 and OS01 to 45% at IS03 (Table 4.2). These fragments were typically composed of mollusk, echinoderm, and foraminiferal material. The only identifiable fossils were contained in the specimen from IS01 which contained fossil valves of Pecten eboreus. These shells are Pliocene to,early Pleistocene in agq, and are@ found in the Bears Bluff and Waccamawformations of 6-oastal South Carolina. Although the general stratigraphic nature of the exposed bedrock on the continental shelf controls the topographic relief in hard bottom areas, the various encrusting and boring organisms which colonize these exposures modify the relief of the rock surface itself. Several organisms commonly found on the rock samples contributed to the complexity of the microhabitat available to other more motile epif auna. These included the -encrusting bryozoans-_(T EM ostega veausta-, Reptadeonella hastingsae, Hippop6rina contracta, Turbicellipora @dichotoma@'@ Schizoporella floridana,_Petjr--al-f_e_1la bisinuata, Hippallosina rostri-gera. Celleporaria albirostris), mollusk shells (Chama sp., Arca zebra), barnacles (Balanus venustus, B. trigonus), stony corals (Solenastrea hyades, Phylla gia americana, Balanophylla floridana), and the calcareous tubes of serpulid worms. A list of the dominant encrusting species found on rocks from each station is included in@@able 4.2'N These organisms produced a moderate to high degree of rugosity on -all rock samples examined. All rock samples also contained either living specimens of the burrowing mussel Lithophaga sp,.. or evidence of their boring activity. Burrows were particularly numerous on rocks from IS02, MS02, and MS03, and specimens from those stations showed the greatest degree of porosity. Table 4.2. Results of thin section analysis and general description of rocks collected by dredges and SCUBA divers at live botffflrstations. Petrographic Analysis Description of Terrigenous Allochemical Orthochemical Encrusting Boring Station Rock Const ituents ConsLiLuents Constituents Fauna Fauna IS01 Sandy biomicrite Quartz sand Moiltisk fragments: Micrite: 15%. Chama sp. Lithophaga sp. (micrite replaced grains: 40%, 52, 2mm-20mm In light to dark Serpulldae by collophane) poorly sorted, size, replaced by brown Solenastrea hyades sub-angular, fine sparry calcite Collophane: 40%, Trypsosteg@ venusta sand (1/8-1/4 mm) replaces the Reptadeonella hastingsae micrIte IS02* Moderately to Quartz sand grains: Mollusk and echino- Micrite: 7%-37% Chama sp. Lithophaga sp. strongly dolomi- 22%-351, poorly derm fraRments: Dolomite: 20%-46% Serpultdae tized sandy sorted, sub-angular 9%-10% (also some appears to have Phyllangla americana biumicrite to sub-rounded, fine foraminifers, bryo- replaced the Balanus trigonus to medium sand zoan, and coral micrite Arca zebra material) Phosphatic Hippoporina contracta concretions: 1%-4% Turblcelllpora dichotoma 41- .IS03 Blomicrite Quartz sand grains: Fossil fragments: MIcrIte: 50%, Chama sp. Lithophaga sp. 5%, well sorted, 45%, 2mm-10mm light to dark Serpultdae angular, very fine size, partially brown Phyllangla americans sand (1/16-1/8 nun) micritized and Balanus trigonus replaced by sparry Balanus venustus calcite Schizoporella sp. HS01 Sandy blomicrite Quartz sand grains: Fossil fragments: Micrite: 30%. very Chains sp. Lithophaga sp. 35%. poorly sorted, 35%, mollusk, light brown, Serpulldne sub-rounded to sub- echinoderm, and crystalline (< 10 Balanophylls florldana angular. fine sand foraminiferal lim, but much Balanus sp. (1/8 - 1/4 mm) material, 1-5 mm greater than crypto- Petrallella bisinuata crystalline micrIte) Schlzoporella florldana MS02 Sandy biomicrite Quartz sand grains: Fossil fragments: Micrite: 20%, dark Chams sp. Lithophaga sp. 40%, poorly sorted. 40%, mollusk, brown, partially Serpulidne sub-angular to sub- echinoderm, and recrystallized to Balanus 9p rounded, fine sand foraminiferal fine-grained Coralline algae (1/8 - 1/4 mm) material, 1-5 nun sparry calcite Hippallosina rostrigera adjacent to terri- Trypsostega venusta genous and allo- chemical sand grains mmvw@ W 6060601"M mom Table 4.2 (Continued) Petrographic AnalyslS Description of Terrigenous Altochemical Orthochemical Encrusting Boring Station Rock Constituents Constitutents Constituents Fauna Fauna NS03 Phosphatic sandy Quartz sand Fossil fraginents: Micrite: 50%, Chama sp. Lithophaga sp. biomicrite grains: 20%, 20%, mollusk, dark brown Serpulidae poorly sorted, echinoderm, and Balanus sp. sub-angular to foraminiferal Trypsostega venusta sub-rounded, material, 1-2 mm - Celleporaria albirostris flite sand (1/8 - Petrallella bisinuata 1/4 mm) Phosphorite sand grains: 10%, well sorted, rounded, very fine sand (1/16 - 1/8 nun) Osol Quartz sandstone Quartz sand Fossil fragments: Micrite: 15%, Chama sp. Lithophaga sp. with micrite grains: 65%, very 20%, mollusk and dark brown Serpulldae cement poorly sorted. foraminiferal Balanophylla florldana sub-rounded to material, 1-5 mm Undetermined corals sub-angular, Balanus sp. coarse to fine Undetermined bryozoans sand (1/8 1 mm) *based on thin sections from 974 44 DISCUSSION The literature indicates that low relief areas (< 0.5 m profile) typically support sparse to moderate growth of sessile epibenthos (mostly sponges and octocorals), and are widely distributed across the shelf (Henry and Giles 1979, Hen y et al.1980, Powles and Barans 1980). Due to their low relief, these areas aretot often detected by fathometer or side scan sonar. Consequently, because television surveys on the shelf have been rather limited, regional distribution of these areas is largely unknown. Two inshore stations of the present study (IS01 and IS03), one middle shelf station (MS02), and one outer shelf station (OS01) fall into the low relief category. Another middle shelf station (MS03), for which videotape analysis indicated extensive areas of low relief, but where scuba observations revealed at least some local areas of moderate relief, illustrated the overlap of these morphological categories. In fact, all live bottom areas examined in this study exhibited a gradient in the degree of relief which results in some overlap of classification. All low relief stations showed evidence of a hard substratum in areas where outcroppings were not detected, by the growth of attaching organisms that extended through the layer of sand. Figure 4.11 is a photograph of a typical .low relief hard ground obtained by scuba divers. This type of substratum was present at most study sites to varying degrees, but was prevalent at IS01, where the bottom was generally devoid of rock relief. Another example of low relief live bottom, with areas of patchy rock outcroppings less than 0.5 m in height, is shown in Figure 4.12. Powles and Barans (1980) investigated the groundfish in a hard bottom area encompassing station IS01. They reported a flat, sandy substratum under- lain at various depths by rock and described areas of bare sand alternating with areas of thick epifaunal growth. This patchiness was probably attribu- table to sediment depth, since organisms were found attached in depths of 8 cm and less, but not in sand 15 cm thick. Henry and Giles (1979) have also attributed the unpredictability and patchiness of hard ground distribution to sediment thickness. It is likely that low relief areas are subjected to cyclic covering and uncovering by a layer of sand several centimetres or more in thickness. This temporal variability of low relief live bottom areas may be significant (Powles and Barans 1980). Moderate relief reefs from 0.5 m to 2 m are common off northern Florida, South Carolina and North Carolina, and occur at inner and middle shelf depths between 15 m and 30 m (Henry and Giles 1979). Although many inshore reefs typically are of low relief (Henry et al. 1980, this study), one notable exception is the 40-km2 area known as Gray's Reef which encompasses station IS02. Although a maximum relief of 6.6 m has been observed (Hunt 1974), the relief is generally less than 2 m, and it is a characteristic moderate relief reef (Henry et al. 1980). Middle shelf stations MS01 and MS03 were also classified in the moderate relief category, and Figure 4.13 shows a ledge at MS01 that is typical of this category. A third classification of hard ground, the shelf edge reef, was described by Henry and Giles (1979) as a discontinuous, but generally well defined, high relief ridge or series of ridges at or near the shelf break. This,series of ridges extends from Cape Hatteras, North Carolina, to Ft. Lauderdale, Florida (Macintyre and Milliman 1970, Avent et al.-1977) and is characterized by blocky irregular rock outcrops with local relief up to 15 m (Henry et al. 1980). Although relief this great was not detected during videotape analysis, additional videotapes from OS02 and OS03 showed areas of relief considerably Vn '41 U1 "ev-, ZI , Nu 7: I Figure 4.11. A live bottom station with typical low relief hard ground covered by an extensive layer of sand. Finger-like projections are the octocoral Titanidium frauenfeldii. The smaller, branching octocorals are probably Lophogorgia hebes. The actual distance across the middle of the photograph is about 3.0 4.5 m. MMM man M MM M M M M M MM M M W Figure 4.12. A live bottom station with patchy outcroppings of low relief. A vase sponge, Ircinia sp., is evident in the lower portion of the upper left-hand corner. The highly branched octo oral Muricea pendula can be seen on the far right, in the middle of the photograph. The @ctual distance' across the middle of the photograph is about 7.6 m. 47 MI Figure 4.13. A ledge of moderate relief at a live bottom station. Note the large vase sponge, Ircinia campana, in the upper right- hand portion of the phCtograph. Length of the stick held by the diver is 1 m. 48 greater than 2 M. Rocks shown in still photographs at these two stations were similar in shape and size to the blocks described by Henry et al. (1980). Water depths at all outer shelf stations (Table 4.1) were also similar to the 50 - 71D m depths at which Henry and Hoyt (1968) encountered shelf edge reefs. Stations'OSO2 and OS03 had numerous ledges and rock outcroppings (Figures 4.8 - 4.10), but relief at OS01 was similar to low relief stations (Figures 4.7 and 4.10). Station OS01 was located landward of what Henry et al. (1980) described as a transitional zone in which no distinct scarp was present. Their records, compiled from fathometer data along the shelf edge, also indicated the presence of a pronounced scarp near OS02 and OSO3. Television reconnais- sance and videotape made at both of these stations suggest that they lie within narrow, elongated features which may be more extensive than the areas delineated for this study (Figures 4.8 and 4.9). Estimating the amount of live bottom habitat that occurs on the continental shelf is difficult because of the patchy and discontinuous nature of its distribution. Several studies have attempted to make such assessments of live bottom coverage, but the accuracy of these estimates is uncertain. Henry et al. (1980) estimated the proportion of hard bottom in the Georgia Bight to be 4.3% of the total area surveyed, but they consider this to be an underestimate - because an additional 16.2% of shallow acoustic reflector may support undetected low relief hard bottom. Limited television groundtruthing did not confirm this, however. More recent studies by Parker et al. (in preparation) suggest that "rock-c-oral-sponge" habitat accounts for nearly 30% of the substratum between the 27--m and 101-m isobaths from Cape Fear to Cape Canaveral. This is equiva- lent to an area of 7403 km2 of live bottom, as compared with the estimate of 6524 km2 derived by Barans and Burrell (1976) for the same area, although the latter estimate was based on a more restricted bathymetric zone (19 - 55 m). Within discrete areas of live bottom, such as our study areas, bottom type is quite variable. The proportion of live bottom within our stations ranged from 25% to 100% of the total area (Figure 4.10). These values may be somewhat inflated, since the presence of even the slightest amount of live bottom within a 10-sec videotape interval qualified that interval as "live"; however, these estimates do document the presence of non-live bottom and the variability between stations. The high variability of our estimates (Figure 4.10) also illustrates the patchiness of the bottom within the study areas. One apparent trend seen in Figure 4.10 is the greater incidence of emergent rock at the offshore stations OS02 and OSO3. This i-s consistent with iEe--pifterns described by Henry and Giles (1979), who suggested that reefs and hard grounds are less common near shore as a result of greater thickness of Quaternary sediments and partial removal of the hard layer by stream channeling during periods of lower sea level. Further offshore the sediment layer thins, allowing increased exposure of underlying hard bottom. Thin section analysis of rock specimens revealed a strong similarity among inner and middle shelf stations. Reef material from these stations consists of sandy_,li estones that ar.e.-classified as sandy -biomicrites (Table 4.2). Hunt (1974) found that the reef substrate at Gray's Reef (IS02) consists of an outcropping layer of sandy biomicrite. However, unlike specimens from the present study and others (Continental Shelf Associates 1979), Hunt's specimens were strongly dolomitized following deposition of the rock in a shallow marine environment. Hunt (1914) suggested this layer may be strati- graphically continuous over an extensive area and correlated it with the Duplin Marl of coastal Georgia and northern Florida. Rock samples collected in 49 shallow water near IS01 by Powles and Barans (1980) also consisted of a tightly cemented limestone conglomerate of carbonate shell and quartz sand material. Petrographic analysis by Continental Shelf Associates (1979) on more than 40 dredge samples from off South Carolina and Georgia have shown that the hard bottom was primarily a n- t__---to- suLVZ;__f_ec-e_n@-t_ b_f_os@ir_om_a__1_ -r-e-e-f- ---)somewhat younger thal indicated by Hunt (1974Y '- @ ROG @i @arr@p@e@i f i 6m@a - @ - -ed g e r e e f 1 y i n g east of Charleston in 44 - 78 m depths, were predominantly sandstone (Contin- ental Shelf Associates 1979), as was the single specimen from station OS01 (Table 4.2). The lack of rock samples from the other two outer shelf stations, OS02 and OSO3, precludes speculation on the significance of the distribution of lithologic types among the study areas. IMPACT /ENHANCEMENT Because our assessment of the physical characteristics of each study area was limited, only general statements can be made concerning possible impacts of drilling operations. One potential negative impact would be environmental damage associated with increased sedimentation over hard bottom. However, enhancement of these live bottom areas also could result from the addition of hard platform surfaces. Increased sedimentation resulting from discharge of drilling muds and cuttings would be less severe where currents are strong enough to disperse these materials over a wide area. For example, effects of drilling activities might be minimal at the shelf edge because of dispersion by the Gu@f Stream. Furthermore, greater relief on shelf edge reefs may localize the effects of sedimentation by confining its accumulation to local depressions. Thus, topographic elevations might remain relatively free of sediment, providing clear surfaces for attachment of encrusting organisms that cannot tolerate even thin layers of sediment. Low relief hard grounds might be more susceptible to widespread burial by drilling discharges, unless tidal currents or occasional storm generated wave action were sufficient to disperse those by-products. Drilling structures present vertical surfaces of solid material and are, therefore, favorable for growth of encrusting epibenthos that require exposed hard surfaces for attachment and growth (i.e., bryozoans, barnacles, some sponges, and tunicates). Growth of such organisms would result in a considerable addition to the fauna in areas where little emergent rock occurs naturally, such as ISO1, IS03, MS02, and MS03. At deeper stations, platforms would also foster the growth of shallow water epibenthic organisms which might otherwise be excluded from the deeper bathymetric zones. CONCLUSIONS - The distribution of live bottom on the continental shelf of the Georgia Bight is not well known, due to the difficulty of recognizing its presence using standard geophysical techniques and equipment. Remote sensing by underwater television and still camera equipment aids in the assessment of bottom type, and was used in the present study to confirm that all study areas.were located over live bottom. - Inshore stations IS01 and IS03 contained patchy live bottom with low relief (< 0.5 m). At IS01 the rock was typically covered by a layer of sand. Station 50 IS03 more closely resembled IS02, which was part of an extensive moderate relief area known as Gray's Reef, and was atypical of inshore reefs. Ledges and rock outcrops in this area were higher and more frequent than at the other two stations. One middle shelf station, MS02, was classified as a low relief hard ground and -possessed only low, rounded outcroppings. At the other middle shelf stations, ledges of moderate relief (0.5 - 1.0 m) were found. At MS01 these ledges were extensive, but they were somewhat localized at MS03. Outer shelf stations were located near the continental shelf break, and OS02 and OS03 had numerous ledges with moderate to high relief (> 0.5 m) and outcroppings of large rectangular rocks. These two stations may be a part of a long series of discontinuous scarps that extend along the shelf edge from North Carolina to Florida. OSOI was unlike the other outer stations and had less emergent rock and lower relief, The distribution of live bottom within the study sites was extemely patchy. This patchiness is reflected by high variability among estimates of frequency of occurrence of hard bottom, which ranged from 25% to 100%. Analysis of videotapes for bottom type revealed no trends, with respect to depth or latitude, in the proportion of live bottom versus non-live (sand) bottom, and still photograph analysis supported this conclusion. Emergent rock was found at all stations, although it was generally less frequent at inshore stations versus offshore stations, where it accounted for up to 40% of the substratum. Rock samples collected at inner and middle shelf stations were of similar composition, consisting of heavily encrusted fragments of sandy biomicrite. The only rock specimen obtained from the outer shelf depth zone was a quartz sandstone rock from'OS01. All rocks collected were rugose, heavily encrusted by epifaunal organisms, and showed varying degrees of bioerosion by boring organisms. This study has provided only limited information for predicting impacts on the physical characteristics of live bottom habitats. However, it is likely that negative impacts would be related to excessive sedimentation caused by disposing drilling muds and cuttings. One potential benefit of oil platforms would be the-additional hard substrate made available by emplacement of these structures, particularly in areas where most hard surfaces are normally covered by a veneer of sand. 51 CHAPTER 5 BENTHIC COMMUNITY INTRODUCTION Marine epifaunal communities associated with intertidal and coastal shallow water hard substrates, such as rocks and shells, have been the subject of intensive theoretical and empirical investigations (see Osman 1977 for review). However, studies concerning epifauna associated with oceanic hard bottom habitats have lagged behind those conducted in the more accessible intertidal zone. This is unfortunate because oceanic hard or live bottom communities are highly diverse and ecologically important to offshore fisheries in the South Atlantic region (Struhsaker 1969, Miller and Richards 1979). One of the primary goals of the current investigation is to characterize the epi- benthos from representative live bottom habitats. The information provided herein will serve as a basis for predicting community composition and structure at other live bottom habitats in the South Atlantic and should be useful in management decisions concerning oil and gas exploration on the continental shelf. Although several previous studies have examined biota associated with live bottom habitats on the South Atlantic continental shelf (Pearse and Williams 1951, Menzies et al. 1966, Macintyre and Pilkey 1969, Macintyre 1970, Huntsman and Macintyre 1971, Cain 1972, Hunt 1974), most have been limited to descriptive lists of fauna present in discrete areas of the shelf or have centered on selected taxonomic groups. A community approach to the study of the hard bottom habitat was not forthcoming until McCloskey's (1970) paper. Later, Schneider (1976) considered spatial and temporal distributions of benthic marine algae from hard bottom areas of the middle and outer continental shelf of North Carolina. More recently, studies by George and Staiger (1978), Henry et al. (1980), and Powles and Barans (1980) have documented the location and extent of some live bottom habitats on the continental shelf and provided generalized characterizations of these sites. In addition, Continental Shelf Associates (1979) compared hard -bottom communities present at four sites in different bathymetric zones; however, their assessment of community composition was secondary to the physiographic characterization of these hard bottom sites. This study provides comprehensive information on the epibenthic communities associated with several hard bottom sites on the shelf between South Carolina and northern Florida. Our goals are to describe the composition of the communi- ties in terms of seasonal, latitudinal, and bathymetric. variations; to adequately understand the structure of the community in terms of species abundance and distributional patterns; and to propose hypotheses concerning the effect of physical disturbances on community structure. METHODS Laboratory Analysis: Television Transects - Videotaped segments of television transects used 52 in the bottom type analysis (described in Chapter 4) were also used to esti- mate the frequency of occurrence of large fauna and flora. Epibenthic taxa analyzed in this effort included the sponges Spheciospongia vesparium, Ircinia campana, and Haliclona oculata; soft corals Leptogorgi@,spp., Titanideum frauenfeldii, Muricea pendula, Lophogorgia hebes, and Stichopathes sp.; hard corals Oculina spp. and Solenastre2, hyades; and algae. lEstimates of frequency of occurrence were obtained for the above species by nbting the presence or absence of each species during 10-sec intervals along the transect paths. Assessments made during each interval were restricted to the center third of the television monitor to minimize variability in estimates due to poor water visibility and also, to minimize variability in bottom sur- face area assessed due to variations in the height of the camera above bottom. When poor visibility made it impossible to accurately determine the presence or absence of a certain species during an interval, the interval was not in- cluded in the frequency estimate of that species. Thus, frequency estimates represent the proportion of intervals in which a species was present relative to the total number of intervals analyzed for that species along a transect. Still Camera Transect Analysis - Selected slides taken 1 m and 3 m above the bottom during still photographic transects (see Chapter 4 for details on selection) were analyzed in the laboratory using different techniques. Slides obtained from 1 m above bottom were projected onto a screen to provide an image of 0.5-m2 bottom surface area for quadrat analysis. Quadrat boundaries were drawn on the screen and measurements of real bottom area were derived using known measurements of the tripper weight in each photograph. A 0.5-m2 quadrat represented the maximum bottom surface area available for analysis. Biota observed in each of the 25 replicate slides was evaluated using the random point count technique described by Bohnsack (1979). Fifty points were selected in each slide from which estimates of percent cover were taken. In some instances, fewer than 50 points were analyzed because of poor visibility and obstruction of bottom by the tripper weight. Identifiable organisms which were observed in the slides, but not under points, were also noted. Slides obtained from 3 m above bottom were projected onto a screen to provide a quadrat image of 3 m2' the maximum bottom surface area available for analysis. Since only larger fauna were generally visible in these slides, analysis entailed counting the number of each species observed in the quadrats and tabulating the presence of colonial organisms which could not be counted. Removal Sampling Gears - In the laboratory, organisms collected in dredge and trawl samples were sorted into the following categories: Algae, Porifera, Hydrozoa, Scleractinia/Octocorallia, Mollusca, Decapoda, Echinodermata, Ascidiacea, and a miscellaneous category for remaining organisms. Selection of these categories was based upon the stated objectives for the trawl and dredge sampling procedure, namely, to characterize the presence of large epifauna and macroalgae. For that reason, several smaller taxa (e.g. Amphipoda, Polychaeta) which were not well sampled by these gears were not sorted from the samples. Except for algae, which was kept in formalin, all specimens were transferred to 70% isopropyl alcohol and identified to the lowest fiasible taxonomic level by the appropriate investigator. Suction and grab samples were obtained to provide quantitative informa- tion on smaller epibenthos not sampled in dredge or trawl gears. Rose bengal stain was added to these samples in the laboratory to facilitate sorting of 53 the small organisms from non-biological material. Prior to staining, macro- algae and sponges that were visible without magnification were removed to avoid destroying characteristics important in the identification of these taxa. Following removal of these organisms and staining, the samples were then sorted under illuminated magnifiers into the following categories: Algae, Porifera, Mollusca, a category for "worm-like" organisms (including annelids, sipunculids, echiurids, phoronids, etc.), Decapoda, Arthropoda (excluding Decapoda), Echinodermata, Ascidiacea, and a miscellaneous cate- gory. Animals were then distributed for identification and 'enumeration of all non-colonial taxa. Encrusting fauna such as bryozoans and barnacles, which were assessed in dredge and trawl samples, were not included in the analysis of suction and grab samples. In addition, the abundance of hydroids and colonial corals was not considered because these organisms are not easily quantified by counting. Representative specimens of all taxa. collected were transferred to separate vials and labelled consecutively with a voucher specimen number. A voucher ledger was maintained which included the following information for all specimens: voucher number, species name (or lowest known taxon), family name, number of specimens, latitutde and longitude, depth, bottom temperature, collection gear, date of collection, collection number, and the name of the individual making the identification. When the container was large enough, a permanent label containing this information was included with the specimens. Most specimens, however, were stored in small vials, and the only information included in the vial was species name, voucher number, and collection number. Data Analysis: Television Transects - Mean frequency of occurrence estimates for the sponges, corals, and algae were computed from occurrence percentages noted on replicate transects. Because the data were proportional, all percentages (P) were transformed using arcsin for a Model I one-way analysis of variance (ANOVA) with stations as treatment groups (Sokal and Rohlf 1969). Removal Sampling Gears - Qualitative binary data (i.e., species presence or absence) collected by dredge and trawl, and quantitative abundance data collected by suction and Smith-McIntyre grab samplers were converted into a standard data format (Appendix 7) prior to data analysis using computer pro- grams. Numerical Classification - Numerical classification (cluster analysis) was used to elucidate patterns of similarity among collections and among species for both binary and abundance data. Due to the large number of species represented in collections made by the various sampling devices, it was neces- sary to reduce data sets which contained > 150 species prior to cluster analysis in order to remain within the computational core and time limits of available computer programs. Data sets were reduced by both elimination of species which were infrequently collected and elimination of these taxa. from our data sets ' of undetermined or questionable identity, unless such species were consistently recognized as being unique. The elimination of these taxa. from our data sets was justifiable because "rare" species usually do not have definable distribu- tion patterns and can confuse interpretation of cluster analysis. Analysis of data sets for dredge and trawl collections included only those species represented in three or more samples. Because the large number of species from pooled suction and grab collections exceeded the capability of our 54 computer program, analysis was restricted to those species which occurred in seven or more samples. Following reduction of species, data sets were examined to insure that each collection contained at least two species. Collections which contained only one species were eliminated because they contribute little information to cluster analysis (Boesch 1973) and fre- quetly confuse interpretation. Both species and collections were classified using clustering methods whid1h are discussed at length by Sneath and Sokal (1973); Clifford and Stephenson (1975); and Boesch (1977). Flexible sorting (Lance and Williams 1967a) was used with a cluster intensity coefficient (a) of -0.25. At this level of $, flexible clustering imposes a bias against an entity or group joining a large group and a bias for entities or small groups to form sepa- rate branches of the hierarchy (Williams 1971, Clifford and Stephenson 1975, Boesch 1977). Flexible sorting with 0 of -0.25 has been satisfactorily used in marine ecology and has become more or less conventional (Clifford and Stephenson 1975). The clustering algorithms differed according to whether the data were qualitative or quantitative. The Jaccard similarity coefficient was used with binary data and species abundance data were subjected to a square-root transformation and subsequently clustered using the Canberra metric similarity coefficient. Normal and inverse classifications were produced for each data set. The result of normal classification is a dendrogram in which collections are clustered as entities with species presence or transformed abundance as attributes, whereas inverse classification produces a dendrogram in which species are clustered as entities with their presence or transformed abun- dance in collections as attributes (Williams and Lambert 1961). The Jaccard similarity coefficient is effective in discriminating dis- tributional relationships among species or collections and is particularly useful when many conjoint presences exist (Clifford and Stephenson 1975, Boesch 1977). This coefficient ranges from zero to one with one expressing maximum similarity or identical entities (species or collections). It is expressed as: a + b + c where a is the number of attributes (joint presences) shared by both entities; b is the number of attributes possessed by the first entity but not the second; and c is the number of attributes possessed by the second entity but not the first. The Canberra metric measure, expressed in terms of dissimilarity, is: Djk = 1 Z JXij - Xik1 m i (Xij + Xik) where D-k is the dissimilarity between entities (species or collections) j and k; m isjthe total number of attributes (transformed abundance); and Xij and Xik refer to abundance of the ith attribute for entities j and k, respectively (Lance and Williams 1967b). The similarity equivalent of this coefficient is: Sjk = 1 - Djk, where Sik is the similarity between entities j and k. The Canberra metric coeffi'cient is not greatly influenced by extremely abundant species which might otherwise dominate the coef f icient (Clif f ord and Stephenson 1975). Hence, this coefficient is appropriate for the purpose of identifying assemblages in the live bottom community which contain numerous rare species. 55 Because the Canberra metric measure is insensitive to large attribute values, it was used with the relatively mild square-root transformation (Clifford and Stephenson 1975). Following formation of dendrograms resulting from normal and inverse classificatioA, groups with internal resemblance were chosen by a variable 11stopping rule" (Boesch 1977) which is based on a priori knowledge of station characteristics and the ecology of component invertebrate species. For some data sets, it was necessary to reallocate misclassified entities from one group to another. The criterion for reallocation involved the computation of average similarity values to determine whether inclusion of reallocated entities improved the average similarity of the group in which it was placed (Boesch 1977). Nodal Analysis - Nodal analyses (Williams and Lambert 1961, Lambert and Williams 1962) were employed to describe collections at a station in terms of their characteristic species and to describe species groups resulting from inverse cluster analysis in terms of their patterns of occurrence in collections (Boesch 1977). Coincidence was expressed by graded constancy and fidelity values in nodal diagrams. Nodal diagrams were drawn so that the width of rows and columns was proportional to the number of entities in the respective station and species groups. Constancy expresses the frequency with which species belonging to a particular group are found in collections which represent a given station It is expressed algebraically as: Cij aij (ni nj) where aij is the actual number of occurrences of members of species group i in collection group J, and both ni and nj are the numbers of the entities in the respective groups. The constancy index has a value of one when all species in a group occurred in all collections at a station and zero when none of the species in a group occurred in collections at a station. The fidelity index: Fij = (aij Ej nj) (nj Ej aij) uses the same terms as the constancy index to express fidelity of species in group i to collections at station j. It measures the degree to which species are restricted to collections at a station. The fidelity index ranges from values greater than two, suggesting "preference" of species in a group for collections at a station, to less than one, which suggests "avoidance" of stations represented by collections. Reciprocal Averaging Ordination - Reciprocal averaging, an eigenvector method of indirect ordination (Hill 1973), was used in conjunction with cluster analysis to describe the zonation of live bottom communities based on data from samples collected by dredge, trawl, suction, and grab. This method involved an iterative process in which species scores, weighted by their position along a rough initial gradient, were used to compute sample scores and vice versa. Reciprocal averaging ordinations were performed on qualitative and quantitative data following reduction and transformation, as previously 56 described for cluster analyses. A further reduction in the number of species to < 100 was required to conform with the dimensions of the program utilized (ORDIFLEX, Gauch 1977). The seven axes extracted by ordination are assigned eigenvalues, expressed as percentages of the total eigenvalue. These percentages indicate the pro- por on of the total variance in the data set accounted for by each of the sev axes. The collection scores resulting from ordination were ranked and resealed from zero to 100 and then plotted separately on the first two axes. Species ordinations were less informative than inverse cluster analyses. Consequently, only collection ordinations were included in this report. Species Diversity - The Shannon index of species diversity (Pielou 1975) and its two components, species richness and evenness, were computed for quantitative collections made with suction and grab samplers. These measures of diversity were also calculated on data from pooled replicates in order to index diversity by station. The Shannon index (H') is expressed by: H' s -E Pi 1092 Pi i=l where s is the number of species and Pi is the proportion of the ith species in a collection. Species richness (SR) was calculated using Margalef's (1958) expression: SR = (s-1) loge n where s is the number of species and n is the number of individuals in a collection. The evenness index (J') was calculated using the following expression from Pielou (1975): JI H' 1092 s Additional sample statistics used to assess differences in community structure among stations included the number of species (s) and number of individuals (n). Both s and n were tabulated for collections made with suction and g-rab samplers, while only s was tabulated for qualitative collections made by dredge and trawl. The Kruskal-Wallis one-way analysis by ranks (Siegel 1956) was used to determine whether s and n differed sig- nificantly between stations. Dominance diversity curves (Whittaker 1965) were drawn using the rank of each species and its corresponding number of individuals from pooled replicated collections made at each station with suction and grab samplers. The degree of dominance at a station was quantified with the dominance index (DI) (McNaughton 1967): DI - Ni + N2 (100) N where N1 and N2 are the numbers of individuals for the first and second most 57 abundant species, and N is the total number of individuals for all species at a station. �Iiecies Abundance - An index of relative abundance (Musick and McEachran 1972, Elliott 1977) expressed as: n 1 E loge (x + 1) n 1 where x is the number of individuals of a given species and n is the number of collections, was used to assess relative abundance of numerically dominant species by station. The data were logarithmically transformed to reduce the variance to mean ratio for number of individuals. Numerically dominant species were chosen arbitrarily as the ten most abundant species from combined data collected with suction and grab samplers during summer and winter. The Mann- Whitney U-test (Siegel 1956) was used to test whether the median abundance of each dominant species differed between winter and summer collections. Biomass - A Model I single classification analysis of variance (Sokal and Rohlf 1969) was performed on biomass determinations from dredge and trawl collections separately to determine whether biomass from replicated sampling effort differed between stations. Due to non-normality and heterogeneous variances, a logarithmic [loglo (x + 1)] transformation was used prior to the analysis of variance. Student's t-test (Sokal and Rohlf 1969) was used to determine whether invertebrate biomass differed between winter and summer sampling periods. Because biomass determinations from samples collected by dredge and trawl were not normally distributed and had heterogeneous variances, a logarithmic [logio (x + 1)] transformation was performed on the data prior to the t-test. The rejection level for the null hypothesis in all statistical tests was a = 0. 0.15. RESULTS Assessment of Epibenthos by Television Transects: Analysis of sponge frequency along television transects (Figure 5.1) indicated several differences in the distributions of the three species monitored. The finger sponge Haliclona oculata was the most commonly observed sponge at inner shelf sites. The occurrence of this species de- creased significantly (P < 0.002, ANOVA) with depth, and it was only rarely observed along transects at middle and outer shelf station. The vase sponge Ircinia campana was the second most common sponge observed at inner shelf sites, and this species occurred more frequently than the other two species at middle and outer shelf sites. Although the percentage occurrence of I. campana varied considerably between stations, no depth related trends were observed, and differences were not highly significant (P > 0.01, ANOVA) due to high intra-site variability. The loggerhead sponge Spheciospongia vesparium was the largest sponge observed at all stations. This species occurred less frequently than the other two sponges at inner shelf sites and was only slightly more common than H. oculata at deeper stations. No significant depth related patterns were detected for S. vesparium. Additionally, no Comparison of Sponge 60- Frequency Along 40- �Ahedosponglo "Speriuln Television Tra'nsects 0 WINTER TRANSECTS 20- SUMMER TRANSECTS 0 W 100- 0 AL- IL N to 6 N C4 to 0 U) 0 U) 0 0 U) W U) z 0 W 0 0 M 80- Irdnia compen Bo- Haticlona oculote 0 60- So- 00 o 0 40- 40- z W 20- 20- D W Ir 0 - I - k h- rh. N " F) g it) N to C4 tL 0 0 0 0 0 8 0 0 0 0 U) V) U3 U) V) U) U) U) V) U) Cn V) U) W 0 0 0 7 0 0 0 STATIONS Figure 5.1. Frequency of three sponqe species alonq television transects durinq winter and summer, 1980. Vertical lines within each bar indicate standard error of the mean. 59 consistent seasonal or latitudinal patterns were noted for any of the above species, except I. campana which was noted more frequently during winter transects at every station. Several distributional patterns are apparent from the analysis of octocorals observed along television transects (Figure 5.2). Leptogorgia spp. occurred quite frequently at inner shelf sites during winter but was only observed at one deeper station (MS01) during this season. This genus was observed at some middle and outer shelf stations during summer, but the frequency of occurrence decreased significantly (P < 0.002, ANOVA) with in- creasing depth. Two species of this genus, L. virgulata and L. setacea, were observed on the transects; however, L. virgid-ata was more common than L. setacea. Data for both species were combined in Figure 5.2 due to the un- certainty of identifications made via television. The most commonly observed octocoral at inner and middle shelf stations was Titanideum frauenfeldii. Frequency of this species differed significantly between sites during both seasons (P < 0.02, ANOVA), but consistent depth related trends were not detected. Lophogorgia hebes and Muricea pendula (presented together in Figure 5.2) were often' difficult to distinguish on the television. However, casual observations made during analysis of the tapes suggest that L. hebes was more prevalent at inner shelf sites, while M. pendula was more prevalent at middle shelf sites. Neither species was commonly observed at outer shelf sites. Frequency estimates were not significantly different between stations where these species were noted (P > 0.2, ANOVA). Consistent seasonal or latitudinal patterns were not detected for any of the above octocoral species. The antipatharian whip coral, Stichopathes sp., was observed only at outer shelf stations, and frequency of occurrence was low. No seasonal or latitudinal patterns were apparent. The only stony corals observed on television transects were the branching coral Oculina sp. and the mound coral Solenastrea hyades. Both occurred very infrequently at the study areas (Table 5.1). High@est f@requency of occurrence for these species was on the inner shelf in winter. Oculina sp. was not collected at any station on.the inner shelf in summer, yet it occurred at all three sites in winter, suggesting that some seasonal pattern may be present. However, any trends are noted cautiously because of the low incidences of these species. 'Undetermined species of algae were also observed infrequently along transects, except at station IS01 and MS01 during summer (Table 5.1). Algae were not observed at outer shelf stations during this season. No lati- tudinal trends were noted for stony corals or algae. Assessment of Epibenthos by Still Camera Transects: Data from the point count census shown in Table 5.2 represent estimates from only those quadrats which showed evidence of hard bottom. Even so, estimated biota cover observed in these quadrats was quite low at all stations, ranging from 3.7% at MS02 to 19.6% at OSO2. However, these percentages may underestimate true biota cover since it was often impossible to ascertain whether biological material was under a particular point. No discernable trends were noted with respect to percentage biota cover and depth or lati- tude. Proportional estimates of bottom cover attributable to major taxonomic groups are presented in Table 5.2, and Table 5.3 lists all biota identified in the 0.5_m2 quadrats at each station. Density estimates of fauna observed in the 3-m2 quadrats (Table 5.4) were also derived, but only from those quadrats with evidence of hard bottom. Unfortunately, the bottom was not visible in quadrats photographed at IS02 Comparison of Coral Frequency Along Television Transectss 0 WINTER TRANSECTS 80 0 SUMMER TRANSECTS NO DATA 100- + 60- Leptogorgid spp. ritonideum frouenfeldii 80- 40- W z 20- 60- W X II Ll 1 11 M r6i rh 40- 0 CQ to 'N to ej to 0 0 0 0 0 0 V) U) 0 V) U) 0 20- so- ON U. Lophogorgid hebeslMuriceo pendulo 0 0 60 ) IN to z U) 0 0 0 0 0 (n U) (n U) Cn U) - I ILI 0 0 0 CY 40- 40- ILI - stichapothes SP. - Ix LL 20- 20- 0 N to (n 0 0 Cn 0 0 (n 0 0 0 0 Cn 0 0 U) 0 0 H U) Cn Cn U) (n Cn En U) Cn (n (n U) 0 0 0 0 0 0 STATIONS Figure 5.2. Frequency of coral alonq television transects during winter and summer, 1980. Vertical lines within each bar indicate standard error of the mean. If 61 Table 5.1. Percent frequency of occurrence for the hard corals Oculina sp. and Solenastrea hyades, and for macroalgae (undetermined), based on television transect analysis at live bottom stations. Mean values (R) and standard error (S.E.) are indicated. Oculina sp. Solenastrea hyades Algae winter summer winter summer winter summer Station 7, I*E* R S*E* 11 I*E* R I*E* 11 S*E* R S*E*, ISM 2.6 1.3 0.0 0.0 11.4 7.4 9.0 4.0 69.9 12.8 IS02 1.8 0.7 0.0 0.0 0.5 0.4 0.7 0.3 13.0 4.9 IS03 11.3 1.7 0.0 0.0 0.0 0.0 0.0 0.0 2.4 1.7 MS01 1.3 0.8 0.3 0.3 0.6 0.7 2.8 1.9 24.0 11.4 MS02 4.2 1.9 0.0 0.0 0.0 0.0 1.4 0.3 5.9 3.9 MS03 1.8 0.2 0.2 0.2 0.4 0.5 0.0 0.0 2.1 1.2 Osol 0.8 0.8 0.0 (?.0 0.0 0.0 0.0 0.0 0.0 0.0 OS02 2.0 0.8 0.6 0.6 0.0 0.0 0.0 0.0 0.0 0.0 OS03 0.0 0.0 0.6 0.6 0.0 0.0 0.3 0.3 0.0 0.0 Table 5. 2. Results from point count analysis of O.5-m2 photographic quadrats taken 1 m above bottom showing percent cover .71"erected taxa. Points with Points with Points with Points with Points with Points with Other Inverte- no biota blota Porifera Octocorallia Scleractinia brates Algae No. quadrats No. points % of % of % of % of % of % of Station analyzed analyzed No. total No. total No. total No. total No. total No. total ISM 23 1050 980 93.3 70 6.7 19 1.8 11 1.6 3 0.3 37 3.5 IS02 18 859 764 88.9 95 11.1 18 2.1 35 4.1 0 0 42 4.9 IS03 20 928 838 90.1 90 9.7 35 3.8 36 3.9 0 0 19 2.0 MS01 20 923 828 89.7 95 10.3 23 2.5 10 1.1 0 0 62 6.7 ON [,a MS02 18 869 837 96.3 32 3.7 4 0.5 5 0.6 0 0 23 2.6 MS03 18 853 769 90.2 84 9.8 30 3.5 7 0.8 2 0.2 45 5.3 OSOl 23 1104 978 68.6 126 11.4 17 1.5 3 0.2 1 0.1 105 9.5 OS02 17 775 645 83.2 130 16.8 3 0.4 2 0.1 0 0 125 16.1 OS03 15 696 624 89.7 72 10.3 3 0.4 0 0 0 0 69 9.9 63 Table 5.3. List of taxa identified in 0.5-m2 photographic quadrats taken 1 m above bottom. x = organisms identified in point-count census, organisms noted in quadrats but not included in point-count census. TAXA ISM IS02 IS03 MS01 MS02 MS03 Osol OS02 OS03 PORIFERA Axinellidae undetermined x Chondrilla nucula x Cinachyra alloclada x x x x x Cinachyra sp. x x Cliona sp. x x x x x x x x Haliclona oculata x HomaxInella waltonsmithi x Ircinia campana x x x x Ircinia felix x IKLIEia sp. x x x x Forifera undetermined x x x x x x x CNIDARIA HYDROZOA Aglacphenia sp. x x Aglacphenia trifida - - - Hydrozoa undetermined - - - x x Nemertesia sp. - - - - - - - ANTHOZOA Antipatharia undetermined - - - - - - - x Diodogorgia sp. - - - - - - - Leptogorgia virgulata x x x - - - - Lophogorgia hebes x x - - Muric@a pendula x - x Octocorallia undetermined x - x Telesto sp. x Titanideum frauenfeldii x x x x x x Renilla reniformis x Actiniaria undetermined x Caryophyllidae x x Balanophyllia floridana Oculi- sp. x ANNELIDA Phyllochaetopterus socialis x x BRYOZOA Amathia sp. x CelleForaria manifica ECHINODERMATA Arbacia punctulata x Asteroidea undetermined - - - - Astropecten articulatus - - - - Astroporpa annulata - - - - Echinoidea undetermined - - - - x Eucidaris tribuloides - - - x Holothuroidea undetermined - - - Isostichopus badionotus - - - x Lytechinus variepatus - UROCHORDATA Ascidiacea undetermined x x x Clavelina picta x Didemnidae x ALGAE Algae undetermined x Coralline algae x 64 Table 5.4. Estimated mean (R) densities and standard deviation (SrD.) of selected species observed in 3-M2 photographic quadrats taken 3 m above bottom at inner shelf stations. Additional miscellaneous invertebrate taxa observed in quadrats are also listed. IS01 IS02 IS03 Quadrats Organisms Quadrats Organisms Quadrats Organisms TAXA analyzed per quadrat analyzed per quadrat analyzed per quadrat R S.D. 5E S.D. R S.D. Porifera Spheciospongia vesparium 12 .17 .39 13 .15 .38 Ircinia campana 12 0 - 13 .31 .75 Haliclona oculata 12 .25 .62 13 .77 1.48 Anthozoa Leptogorgia virgulata 10 .40 .97 10 0 - Lophogorgia hebes 9 0 - 12 0 - Muricea @@j Stichopathes sp. 12 0 - 13 0 - Oculina sp. 12 0 - 13 0 - Solenastrea hyades 12 0 - Z 13 0 - Echinodermata Arbacia sp. 11 0 - 13 .15 .38 Eucidaris tribuloides 12 0 - 13 0 - Asteroidea undetermined 12 .08 .29 13 .15 .38 -------------------------------------------------------------------------------------------------------- Miscellaneous Cliona sp. Titanideum frauenfeldii Invertebrate Titanideum frauenfeldii Halichondria sp. Taxa Keratosa undetermined (not counted) Porifera undetermined Size of taxa and bot4om visibility determined the number of 3-m2 quadrats analyzed. 65 Table 5.4 (Continued) Quadrats MS01 Organisms Quadrats MS02 Organisms Quadrats MS03 Organisms TAXA analyzed per quadrat analyzed per quadrat analyzed per quadrat 5i S.D. 2 S.D. R S.D. Porifera Spheciospongia vesparium 14 0 - 14 0 - 6 0 - Ircinia campana 14 .50 .85 14 .21 .58 6 0 - Haliclona oculata 14 0 - 14 0 - 6 0 - Anthozoa Leptogorgia virgulata 14 .07 .28 14 0 - 6 0 - Lophogorgia hebes) Muricea @j 14 .07 .28 14 .57 1.28 6 0 - Stichopathes sp. 14 0 - 14 0 - 6 0 - Oculina sp. 13 0 - 14 0 - 6 0 - Solenastrea hyades 14 0 - 14 0 - 6 0 - Echinodernata Arbacia sp. 14 0 - 14 0 - 6 0 - Eucidaris tribuloides 14 .07 .28 14 0 - 6 0 - Asteroidea undetermined 14 0 - 14 0 - 6 0 - --------------------------------------------------------------------------------------------------------- Miscellaneous Clavelina gigantea Titanideum frauenfeldii Titanideum frauenfeldii Invertebrate Titanideum frauenfeldii Filograna implexa Clavelina gigantea Taxa Ircinia ramosa Tedania sp. T-orifera undetermined (not counted) Filograna implexa -Havelina gigantea Cliona sp. Cliona sp. Ascidiacea undetermined Porifera undetermined Porifera undetermined Size of taxa and bottom visibility determined the number of 3-m 2 quadrats analyzed. 66 Table 5.4 (Continued) Quadrats OSOl Organisms Quadrats OS02 Organisms Quadrats OS03 Organisms TAXA analyzed per quadrat analyzed per quadrat analyzed per quadrat R S.D. R S.D. R S.D. Porifera Spheciospongia vesparium 11 0 - 25 0 - Ircinia campana 11 .27 .90 25 0 - Haliclona oculata 11 0 - 25 0 - Anthozoa Leptogorgia virgulata 4 0 - 23 0 - Lophogorgia hebes) 3 0 - 23 0 - Muricea pendula Stichopathes sp. 3 0 - 24 .04 .20 Oculina sp. 8 0 - 25 0 - Solenastrea hyades 8 0 - 25 0 - Z Echinodermata Arbacia sp. 4 0 - 24 0 - Eucidaris tribuloides 4 0 - 22 .55 .86 Asteroidea undetermined 4 0 - 24 .04 .20 ------------------------------------------------------------------------------------------------------- Miscellaneous Filograna implexa Filograna implexa Invertebrate Cliona sp. Cliona sp. Taxa Actiniaria undetermined (not counted) Size of taxa and botiom, visibility determined the number of 3-m 2 quadrats analyzed. 67 and OS01, and bottom visibility was poor at several other stations. This problem, combined with the elimination of sand bottom quadrats, greatly reduced the number of photographs analyzed from all stations except OS03- Quantitative assessment of the 3-m2 hard bottom quadrats indicated distributional patterns of the larger fauna which corresponded to qualita- tive television observations. The sponges S. vesparium and H. oculata were observed only at inner shelf sites and ranged in average density from 0.15 to 0.17 and 0.25 - 0.77 sponges per 3 m2, respectively. Ircinia campana was observed at all depth zones, but not all stations. When present, average densities of this species ranged from 0.21 to 0.50 sponges per 3 m2. The larger octocorals L. virgulata, L. hebes, and M. pendula were only observed in quadrats at stations ISOI, MSOI, and MS02. Average colony densities were low (Table 5.4). Colonies of the smaller octocoral Titanideum frauenfeldii were not counted due to difficulties in accurately assessing densities of this species from 3 m above bottom. Echinoderms counted in quadrats included Arbacia sp,, Eucidaris tribuloides, and other undetermined Asteroidea * Arbacia sp. was only noted at IS03; E. tribuloides was observed at MS01 and OSO3. A list of miscellaneous colord-ai invertebrates not counted in quadrats is presented in Table 5.4. Qualitative Assessment of Epibenthos Captured by Dredge and Trawl Sampling: �2ecies Composition - A total of 407 and 357 identifiable taxa were collected by dredge and trawl, respectively, during both seasons. A list of the identified taxa, arranged phylogenetically for each station and sampling gear, is given in Appendices 8 and 9. The phyla represented by the greatest number of identified taxa in dredge collections included the Bryozoa (88 taxa) and Cnidaria (85 taxa). Porifera (67 taxa) and Bryozoa (62 taxa) were the most diverse phyla in trawl collections. Those species which were dominant by virtue of their occurrence in 15 or more dredge collections are listed in Table 5.5. Most of these frequently occurring species were either bryozoans or cnidarians, which reaffirms their general predominance in dredge collections from the live bottom habitats* Cnidarians and bryozoans were also important among the 29 most frequently occurring species in trawl collections (Table 5.6); however, dominants collected by trawl also included several decapod and cirriped crustaceans, as well as echinoderms. Algae were collected infrequently by both dredge and trawl. During the winter cruise, none were collected by dredge, while Ulva sp. and Cladophora sp. were present in two samples collected by trawl. During the summer, Gracilaria sp., Hymenema sp., and unidentified algae were collected in three dredge samples, while Ulva rotundata and unidentfied algae were collected in two trawl samples. Althoug7h Sargassum fluitans and S. natans were collected in winter, and S. fluitans and S. filipendula in summer, these algae are pre- dominantly pelagic and were probably caught at or near the surface. There- fore, we! did not consider these species to be part of the epibentic live- bottom community. Percentage contribution of the major invertebrate groups collected with the dredge did not differ appreciably between inner, middle, and outer shelf stations. During both winter and summer sampling, the Bryozoa and, to a lesser extent, the Cnidaria and Porifera, dominated collections across the shelf in, terms of numbers of species (Table 5.7). The Porifera were important in trawl collections only from inner shelf stations, while Cnidaria and Deca- poda were important at all stations (Table 5.8). The Bryozoa were not a major 68 Table 5.5. Invertebrate species represented in 15 or more dredge collections from both winter and summer, 1980. Species Number of Occurrences H ecium sp. (Cnidaria) 15 Lophogorgia hebes (Cnidaria) 15 Hippaliosina rostrigera (Bryozoa) 15 Aetea anguina (Bryozoa) 15 Antropora tincta (Bryozoa) 15 Campanularia hincksii (Cnidaria) 16 Clytia cylindrica ' (Cnidaria) 16 Dynamena cornicina (Cnidaria) 16 Hebella scandens (Cnidaria) 16 Cribrilaria radiata (Bryozoa) 16 Celleporaria albirostris (Bryozoa) 16 Reptadeonella hastingsae (Bryozoa) 16 Balanus venustus (Cirripedia) 18 Monostaechas quadridens (Cnidaria) 18 Turbicellepora dichotoma (Bryozoa) 22 Kochlorine floridana (Cirripedia) 23 Hippoporina contracta (Bryozoa) 23 Trypsostega venusta (Bryozoa) 23 Balanus trigonus (Cirripedia) 24 Conopea merrilli (Cirripedia) 24 Schizoporella cornuta (Bryozoa) 24 Titanideum frauenfeldii (Cnidaria) 25 frisia sF (Bryozoa) 26 Microporella ciliata (Bryozoa) 28 al 69 Table 5.6. Invertebrate species represented in 15 or more trawl collections from both winter and summer, 1980. Species Number of Occurrences Cliona caribbaea (Porifera) 15 Metapenaeopsis goodei (Decapoda) 16 A2.@phyton muricatum (Echinodermata) 16 Synalpheus townsendi (Decapoda) 18 Balanus venustus (Cirripedia) 18 ClytiA fragilis (Cnidaria) 18 Actiniaria (Cnidaria) 18 Obelia dichotoma (Cnidaria) 19 Schizoporella cornuta (Bryozoa) 19 �Xn@Llpheus longicarpus (Decapoda) 20 Haliclona oculata (Porifera) 21 Thyroscyphus marginatus (Cnidaria) 21 [email protected] (Cnidaria) 21 Trachypenaeus constrictus (Decapoda) 23 Turbicellepora dichotoma (Bryozoa) 23 Celleporaria albirostris (Bryozoa) 23 Pilumnus sayi (Decapoda) 24 Lophogorgia hebes (Cnidaria) 24 Ophiothrix angulata (Echinodermata) 25 Monostaechas quadridens (Cnidaria) 29 Microporella ciliata (Bryozoa) 29 Pteri-i colymbus (Mollusca) 29 Leptogorgia virgulata (Cnidaria) 30 Arbacia punctulata (Echinodermata) 30 Spheciospongia vesparium (Porifera) 32 ConopBa merrilli (Cirripedia) 32 Crisia sp. (Bryozoa). 33 Balanus trigonus (Cirripedia) 38 Styeli plicata (Ascidacea) 39 Table 5.7. Numbers of species and percent of total numbers for major taxonomic groups represented In dredge collections at each station and sampling period. Echino- Hollusca Decapods Por1fera CnIdarta Bryozoa dermsta Cirripedia Tunicata Total Station Season No. % No. % No. % No, % No. % No. No. % Nq- % NUMber isol Winter 5 (5.9) 4 (4.7) 16 (18.8) 25 (29.4) 19 (22.3) 9 (10.6) 5 (6.0) 2 (2.3) 85 Summer 2 (3.2) 3 (4.8) 8 (12.7) 14 (22.2) 19 (30.1) 6 (9.5) 5 (7.9) 6 (9.5) 63 IS02 Winter 3 (3.8) 7 (8.9) 19 (24.0) 18 (22.8) 22 (27.8) 5 (6.3) 4 (5.1) 1 (1.3) 79 Summer 7 (8.4) 4 (4.8) 15 (18.1) 17 (20.5) 23 (27.7) 5 (6.3) 5 (6.0) 7 (8.4) 83 IS03 Winter 4 (6.0) 6 (8.9) 21 (31.3) 10 (14.9) 11 (16.4) 8 (11.9) 5 (7.5) 2 (3.0) 73 Summer 5 (7.8) 1 (1.6) 20 (31.2) 9 (14.1) 13 (20.3) 6 (9.4) 5 (7.8) 5 (7.8) 70 MS01 Winter 1 (4.0) 0 0 11 (44.0) 8 (32.0) 2 (8.0) 3 (12.0) 0 25 Summer 1 (1.6) 1 (1.6) 3 (4.9) 27 (42.2) 28 (43.7) 1 (1.6) 2 (3.2) 1 (1.6) 64 -@J CD MS02 Winter 3 (3.1) 11 (11.2) 9 (9.2) 31 (31.6) 30 (30.6) 8 (8.2) 4 (4.1) 2 (2.0) 98 Summer 6 (8.7) 1 (1.4) 9 (13.0) 18 (26.1) 20 (29.0) 6 (8.7) 2 (2.9) 7 (10.1) 69 MS03 Winter 1 (1.4) 0 9 (12.7) 21 (29.6) 31 (43.7) 4 (5.6) 3 (4.2) 2 (2.8) 71 Summer 6 (6.7) 0 11 (12.2) 28 (31.1) 37 (41.1) 3 (3.3) 4 (4.4) 1 (1.1) 90 Osol Winter 2 (3.1) 2 (3.1) 30 (46.1) 6 (9.2) 17 (26.1) 5 (7.7) 3 (4.6) 0 65 Summer 3 (2.9) 13 (12.6) 16 (15.5) 24 (23.3) 32 (31.1) 6 (5.8) 4 (3.9) 5 (4.8) 103 OS02 Winter 4 (6.3) 8 (12.7) 3 (4.8) 16 (25.4) 26 (41.3) 4 (6.3) 2 0.2) 0 63 Summer 0 0 0 2 (10.0) 17 (85.0) 0 1 (5.0) 0 20 OS03 Winter 24 (12.8) 31 (16.6) 27 (14.4) 36 (19.2) 46 (24.6) 17 (9.1) 4 (2.1) 2 (1.1) 187 Summe r 0 0 0 4 (13.3) 22 (73.3) 1 (3.3) 3 (10.0) 0 30 low W* Jo *V1 a * (00 M me SUP Table 5.8. Numbers of species and percent of total number for major taxonomic groups represented in trawl collections at each station and sampling period. Echino- Molluscs Decapoda Porifera Cnidaria Bryozoa dermata Cirripedia Tunicatp Total Station Season No. % No. % No. z No. % No. No. No. % No. % Number ISOI Winter 6 (7.7) 16 (20.5) 25 (32.0) 15 UM) 1 (1.3) 7 (9-0) 4 (5.1) 4 (5.1) 78 Sumer 2 (3.2) 12 (19.3) 13 (21.0) 14 (22.6) 6 (9.7) 3 (4.8) 4 (6.4) 8 (12.9) 62 IS02 Winter 6 (6.9) 15 (17.2) 16 (18.4) 14 (16.1) 19 (21.8) 7 (8.0) 4 (4.6) 6 (6.9) 87 Summer 9 (10.7) 20 (23.8) 11 (13.1) 18 (21.4) 7 (8.3) 3 (3.6) 4 (4.8) 12 (14.3) 84 IS03 Winter 4 (6.0) 13 (19.4) 18 (26.9) 13 (19.4) 4 (6.0) 6 (8.9) 5 (7.5) 4 (6.0) 67 Summer 3 (6.8) 10 (22.7) 10 (22.7) 6 (13.6) 3 (6.8) 3 (6.8) 2 (4.5) 7 (15.9) 44 MS01 Winter 2 (3.6) 20 (35.7) 8 (14.2) 12 (21.4) 8 (14.2) 4 (7.1) 1 (1.8) 1 (1.8) 56 Summer 2 (2.2) 12 (13.5) 8 (9.0) 25 (28.1) 35 (39.3) 3 (3.4) 3 (3.4) 1 (1.1) 89 MS02 Winter 6 (6.7) 11 (12.3) 11 (12.3) 28 (31.5) 21 (23.6) 4 (4.5) 4 (4.5) 4 (4.5) 89 Summer 1 (1.5) 9 (13.4) 4 (6.0) 24 (35.8) 23 (34.3) 2 (3.0) 2 (3.0) 2 (3.0) 67 MS03 Winter 3 (4.2) 18 (25.3) 7 (9.8) 17 (23.9) 16 (22.5) 6 (8.4) 2 (2.8) 2 (2.8) 71 Summer 1 (2.2) 5 (11.1) 5 (11.1) 13 (28.9) 11 (24.4) 6 (13-3) 2 (4.4) 2 (4.4) 45 OSOI Winter 3 (5.9) 14 (27.4) 4 (7.8) 19 (37.2) 6 (11.8) 2 (3.9) 2 (3.9) 1 (2.0) 51 Summer 7 (5.4) 21 (16.0) 21 (16.0) 26 (20.0) 35 (26.9) 6 (4.6) 7 (5.4) 7 (5.4) 130 72 constituent of trawl collections from the inner shelf. The number of identifiable taxa (_S) collected at each station also did not show any consistent pattern with regard to depth, although the most diverse assemblages sampled by dredge and trawl were collected on the outer shelf. 'Among dredge collections, s was greatest at OS03 in winter (Figure @5.3)@ whereas among trawl collections, the richest assemblage of taxa occurred in spimmer at OS01, which was the only outer shelf station sampled by trawl (Figure 5.4). Qualitative samples from inner and middle shelf stations did not-differ appreciably with respect to species number, regardless of the sampling gear used. The Mann-Whitney U-test indicated that s was not sig- nificantly different between winter and summer sampling periods for collections made with either dredge or trawl (P > 0.05). Biomass - Determinations of biomass for individual taxa indicated that the Porifera were dominant at most stations sampled during winter and summer. They constituted 77% of the total invertebrate biomass in winter dredge collections and 66% in summer dredge collections. Among trawl samples, the Porifera accounted for 93% and 84% of the total invertebrate biomass during winter and summer, respectively. For dredge collections, the only exceptions to dominance of biomass by Porifera occurred at stations MSOI, OS01, and OS02 during winter; and IS02 and OS02 during summer (Table 5.9). Videotapes and underwater television indicated that station OS02 in summer was characterized by rocks and shells with very little attached epifauna. Porifera dominated by weight in all trawl collections (Table 5.10). Analysis of variance of logarithmically transformed biomass determinations from replicated dredge samples indicated no significant difference in biomass between stations during winter (P > 0.25) or summer (P > 0.50). However, there were significant differences between stations in biomass of trawl collections (winter, P < 0.01; simmer, P < 0.01). In winter, average biomass was greatest at station IS03 (5E = 105.25 kg) and lowest at station OS01 (R = 0.73 kg). In summer, average biomass was highest again at an inner shelf station, IS02 (R = 41.09 kg) and was lowest at MS02 (R = 1.06 kg). No significant differences were noted in logarithmically transformed biomass determinations between winter and simmer using either dredge (P > 0.50, t-test) or trawl data (P > 0.20, t- test). Species Assemblages and Distributional Patterns: Dredge Collections Normal cluster analysis indicated that stations sampled by dredge were grouped fairly distinctly according to their ba-thymetric location on the continental shelf. The 19 dredge collections obtained during winter were classified into four station groups (Figure 5.5). These station groups corresponded to inner shelf collections (group 1), middle shelf collections (groups 2 and 3), and outer shelf collections (group 4). Collections from inner and outer shelf stations were strongly similar within their respective station groups; how- ever, collections from middle shelf habitats formed two separate groups, with those from station MS01 differing in species composition from collections at stations MS02 and MS03. An examination of the invertebrate species collected at station MS01 revealed that fewer species were found there than at the other middle shelf stations, probably because of poor collections in both eplicate dredge tows. Based on the structural hierarchy of the dend---_- , rt is apparent that middle and outer stations were more similar in faunal composi- tion to each other than to inner stations. Summer dredge collections again grouped into three agglomerations corresponding to inner, middle, and outer shelf stations (Figure 5.6). In 73 34* so* South Carolina DREDGE .,::.INVERTEBRATES @-34' 120- Cr 0) so- 40- W 3: U) LEI OISOI A ANN H MS01 OOSOI 820 OMS02 Georgia 32* OS02 OIS02 B UNSWIC MS03 OOS03 GIS03 JACKSONVILLE- so* x. Figure 5.3. Number of species collected at each station by dredge during winter and summer, 1980. 74 34* 800 South Carolina TRAWL .@34* d 120- 0- -CHARLESTON... a. o-na OIS01 320 :SAVANNAH MS01 OM OOSOI S02 Georgia 320 *OS02 ...... OIS02 BRUNSWItK OMSO5 IL OOSO3 OIS03 JA ONVILLE,-*..... 800 L Figure 5.4. Number of species collected by trawl at each station during winter and surTner, 1980. 75 Table 5.9. Percent of the total biomass for major taxonomic groups in dredge collections for each station and sampling period. The mean M and standard deviation (S.D.) of the total biomass, and the number of samples (n) for which biomass measurements Were taken, are indicated. TS01 TS02 TqQ1 MS01 MS02 MS03 Osol OS02 OS03 WINTER Forifera 82% 36% 64% 0% 93% 82% 2% 0% 62% Anthozoa 5% 13% 12% 10% 3% 0% 2% 0% 0% Molluscs 2% 4% 5% 0% 0% 0% 70% 0% 28% Decapoda 0% 0% 0% 02 0% 0% 0% 0% 2% Echinodermata 9% 10% 13% 90% <1% 15% 202 2% 6% Ascldiaceia 0% 33% 4% 0% 2% <1% 0% 0% 3% Other Invertebrata 2% 4% 1% 0% 1% 3% 7% 98% 0% Total Biomass (kg) 5E 8.03 4.28 3.73 0.10 14.85 6.07 0.46 0.92 3.82 S.D. 6.12 1.23 2.93 0.04 24.47 5.72 0.55 1.54 4.66 n 2 2 2 2 3 2 2 3 2 SUMMER Porifera 45% 30% 85% 62% 78% 87% 55% 0% Anthozoa 24% 4% 5% 3% 4% 7% 35% - 0% Molluscs 16% 0% 02 02 02 1% <12 - 0% Decapoda 0% <1% <1% 13% <1% 0% 1% - 0% Echinodermata 5% 1% 7% <1% 9% 2% 7% - 100% Ascidiacea 7% 65% 32 10% 2% 0% 0% - 0% Othe r Invertebrata 3% <1% <12 12% 4% 3% <1% - 0% Total Biomass (kg) i 2.81 12.10 12.36 1.29 5.71 9.66 1.65 - 0.04 S.D. 3.68 16.11 0.17 0.65 7.53 12.22 0.79 - - n 2 2 2 3 2 2 2 2 1 76 Table 5.10. Percent of the total biomass for major taxonomic groups in trawl collections for each station and sampling period. The mean (j) and standard deviation (S.D.) of the total biomass, and the number of samples (n) for which biomass measurements were taken, are indicated. IS01 IS02 IS03 MS01 MS02 MS03 OSO1 WINTER Porifera 87% 69% 992 80% 96% 94% 71% Anthozoa 2% 2% <1% 0% 2% 4% 3% Molluscs <1% 0% <1% 0% <1% 0% 0% Decapoda <1% <1% <1% 1% 02 <1% 12% Echinodermata 3% <1% <1% 3% <1% <1% 0% Ascidiacea 6% 27% <1% 1% <1% <1% 0% Other Invertebrata 2% 2% <1% 14% <1% <12 14% Total Biomass (kg) i 10.34 26.17 105.25 6.35 31.37 38.37 0.73 S.D. 6.23 23.48 119.54 9.88 43.64 37.11 1.22 n 6 6 6 6 6 6 6 SUMMER Porifera 92% 75% 96% 512 45% 96% 64% Anthozoa 1% 1z 1% <1% 16% 0% 1z Molluscs <1% 12 <1% 1% <1% 0% <1% Decapoda <1% <1% <1% 27% 13% <12 52 Echinodermata <1% <1% <12 1% 16% <1% 20% Ascidiacea 6% 18% 2% 4% 5% <1% 0% Other Invertebrata <1% 5% <1% 16% 5% 3% 10% Total Biomass (kg) i 13.27 41.09 35.54 5.39 1.06 18.60 4.96 S.D. 12.02 20.69 47.22 4.54 1.31 27.86 3.03 n 6 6 5 6 6 6 6 77 Dredge: Station Groups SIMILARITY 8 .6 .4 .2 0 2 Group Station IS03 IS02 Isol isol Isoz IS03 hi-S o F _Msol - - - MS02 MS02 3 MS02 MS03, - -MS03 OS02 osol 4 OS02 osol OS03 OS03 .8 .6 .4 .2 0 -.2 SIMILARITY Figure 5.5. Normal cluster dendrogram of winter dredge collections indicating station groups formed using the Jaccard similarity coefficient and flexible sorting. 78 Dredge: Station Groups SIMILARITY .3 Group Station'l I isol IS02 IS03 IS03 IS02 IS01- MSO I MSO I MS02 MS03 MS03 MS02 U-Sol- OSO1 OS03 OS02 OS02 SIMILARITY Figure 5.6. Normal cluster dendrogram of sunimer dredge collections indicating station groups formed using the Jaccard similarity coefficient and flexible sorting. 79 contrast to the dendrogram. generated from winter dredge data, this cluster hierarchy indicated that faunal composition of all collections from the middle shelf were more similar to the inner shelf collections than to those from the outer shelf. The results of reciprocal averaging ordination basically confirmed the zonation patterns indicated by cluster analysis. For winter data, axis 1, which accounted for 16.57% of the total variance, separated inner shelf (i.e., members of normal cluster group 1) from middle and outer shelf stations (i.e., members of cluster groups 3 and 4, respectively)(Figure 5.7). As in cluster analysis, the greater similarity in faunal composition between middle and outer shelf collections (versus middle and inner shelf collections) is reflected in the greater proximity of the former two groups and in their mutual separation from inner shelf collections on axis 1 (Figure 5.7). Axis 2 accounted for 11.12% of the total variance and separated outer shelf (group 4) collections from middle shelf (groups 2 and 3) collections. Inner shelf collections were generally intermediate in position along axis 2, but they spanned a wide range of values. Unlike cluster analysis, ordination results indicated that collections from MS01 were not sufficiently different from other middle shelf collections to justify separation. This discrepancy in results; of the two analyses indicates the greater space dilating properties of clustering techniques such as flexible sorting as compared with reciprocal averaging ordination. Ordination of summer dredge data indicated a relatively discrete grouping of collections belonging to each of the three shelf areas in ordination space and conformed with the results of normal cluster analysis. Axis 1, which accounted for 19.34% of the total variance, separated outer shelf collections (i.e., members of cluster group 3) from inner and middle shelf collections (i.e., members of cluster groups 1 and 2, respectively)(Figure 5.8). Axis 2, which explained 14.35% of the total variance, was most successful in separating inner shelf collections from middle and outer shelf collections (Figure: 5.8). As demonstrated by cluster analysis, the middle shelf samples taken in the slimmer were more similar to inner shelf than to outer shelf samples. Inverse cluster analysis of the 122 most frequently occurring species collected in winter dredge samples formed ten species groups (Table 5.11). The distribution of species within these groups was compared in nodal dia- grams to determine their relative constancy and fidelity to collections at each station (Figure 5.9). The hierarchy of species groupsformed by inverse analysis and shown in the nodal diagram indicated that species in groups A and B were least similar to other groups in terms of their distributional patterns. These species were primarily associated with collections from the outer continental shelf and exhibited high constancy at those stations. Furthermore, species in these groups were primarily restricted to outer shelf station OSO3. Species in groups A and B which were collected only at outer shelf stations during winter included the bryozoans Plagioecia dispar, Floridina antiqua, and Membraniporella aragoi; the hydroids Salacia7-desmoid-es, Halecium tenellum, and Ey-n--amena dalmasi; the decapod crustacean Mithrax acuticornis; and the echinoderms Narcissia trigonaria and Astroporpa annulata. Species in group C were restricted in their distribution and were highly constant only at inner shelf stations. All species in this group, except the tunicate 'Pyura vittata and the mollusk Simnia acicularis, were collected at all three inne@ -shelf stations. Other species groups formed by our analysis of winter dredge collections ...... ..... 100 A OS021 Cluster 90- Groups 1 0 80- AOSO 1 2 40 3 a 70-,AOS02 OIS01 OIS03 4 A 60- AOS03 OIS02 C\1 250- AOS01 X IMS03 &OS03 A MS02 Olsol CO &MS03 40 MS01 0 40- OIS02 30- IS030 6MSOZ 6MS02 20- 10- 0 0 Msol 16 20 30 410 50 60 TO so 90 100 AXIS I Figure 5.7. Results of reciprocal averaging ordination showing orientation of winter dredge collections at stations on axes 1 and 2. Symbols indicate which group these collections were placed into by cluster analysis. **am 4*W MMI 100 OS02 Cluster Groups go- 60SO2 1 0 .2 0 so- 3 a 70- 60SO3 60SOI WMSOI 60- 0 MS03 MS019 0 CY *MS03 MS02 60SOI 050- 0 MS02 X 40- 00 OIS02 30- OIS01 Olsol 20- OIS03 10- 0 IS02QOIS03 0 10 20 30 @O 5'0 @O -ro 80 90 100 AXIS I Figure 5.8. Results of reciprocal averaging ordination showing orientation of summer dredge collections at stations on axes 1 and 2. Symbols indicate which group these collections were placed into by cluster analysis. 82 Table 5.11. Species groups resulting from numerical classification of data from samples collected by dredge during winter and summer, 1980. (Ar - Arthropoda; Bry - Bryozoa; Ch - Chordata; Cn - Cnidaria; Ech - Echinodermata; Mo Molluscs; Po Porifera). I I Winter 1980 Summer 1980 Group A Group A Plagioecia dispar (Bry) Eucidaris tribuloides (Ech) Floridana antiqua (Bry) Smittina smittiella (Bry) Smittipora levinseni (Bry) Filellum serratum (Cn) Stylopoma informata (Bry) Diaperoecia floridana (Bry) Cleidochasma. porcellanum (Bry) Smittipora levinseni (Bry) Cribrilaria floridana (Bry) Cleidochasma. porcellanum (Bry) 'Fi-croporella umbracula (Bry) Poecilosclerida H (Po) Group B Halecium tenellum (Cn) Group B Salacia desmoides (Cn) Mit@-ra-x acuticornis (Ar) Stylopoma informata (Bry) Pachycheles rugimanus (Ar) Cycloperiella rubra (Bry) Halecium tenellum (Cn) Floridina antiqua (Bry) Dynamena dalmasi (Cn) Kochlorine floridana (Ar) Narcissia trigonaria (Ech) Cribrilaria radiata (Bry) Cycloperiella rubra (Bry) Parasmittina spathulata (Bry) Parasmittina spathulata (Bry) Stephanoscyphus sp. (Cn) Group C Astroporpa annulata (Ech) Membraniporella aragoi (Bry) Membranipora tenuis (Bry) Scypha barbadensis (Po) Parellisina curvirostris (Bry) Ophiostigma isacanthum (Ech) Hippaliosina rostrigera (Bry) Eucidaris tribul@Ti@des (Ech) Nolella xigantea (Bry) Aglaophenia latecarinata (Cn) Clytia cylindrica (Cn) Halopteris sp. (Cn) Antropora tincta (Bry) Ircinia strobilina (Po) Group C Amathia distans (Bry) Bimeria humilis (Cn) Encope michelini (Ech) Amathia alternata (Bry) Pyura vittata (Ch) Aglaopl@enia -trifida (Cn) Simnia acicularis (?) (MO) Telesto sanguinea (Cn) Homaxinella waltonsmithi (Po) Oculina arbuscula (Cn) Group D Leptogorgia virgulata (Cn) Arbacia punctulata (Ech) Hebella venusta (Cn) Spheciospongia vesparium (Po) Chaperia sp. (Cn) Lytechinus variegatus (Ech) Aglaophenia allmani (Cn) Scandia muta@b-ilis (Cn) Group D Monost@e-chasaaadridens (Cn) Thyroscyphus marginatus (Cn) Myrastria fibrosa (Po) Aglaophenia latecarinata (Cn) Synalpheus minus (Ar) Hebella scandens (Cn) Cliona caribbaea (Po) Aeverrillia setigera (Bry) Ircinia ramosa (Po) Aetea anguina (Bry) Clavelina picta (?) (Ch) Synthecium tubitheca (Cn) Nellia tenella (Bry) Group E Celleporaria magnifica (Bry) Schizoporellt floridana (Bry) Haliclona oculata (PO) Campanularia hincksii (Cn) Conopea Raleata (Ar) Sertularia marginata (Cn) Membran tenuis (Bry) Hincksella cylindrica (Cn) Hadrom.%:a A (Po) Keratosa D (PW Ciocalapata gibbsi (Po) 'g-alichondria bowerbanki (Po) Group E Pilumnus sayi (Ar) Leodia sexiesperforata (Ech) Conopea merrilli (Ar) Ocnus :yMa:.u: (Ech) Microporella ciliata (Bry) Bala-nu us (Ar) Titanideum frauenfeldii (Cn) 83 Table 5.1.1 (Continued) Winter-1980 S-,-npr 1980 Titanideum frauenfeldii (Cn) Turbicellepora dichotoma (Bry) Epizoanthus americanus (Cn) Schizoporella cornuta (Bry) Telesto fruticulosa (Cn) Balanus trigonus (Ar) Lophogorgia hebes (Cn) Hippoporina contracts (Bry) Telesto sanguinea (Cn) Crisia sp. (Bry) Antropora tincta (Bry) Celleporaria albirostris (Bry) Thalysias juniperina (Po) Arca zebra (MO) Scrupocellaria regularis (Bry) n1a Irci Sa@ana (PO) Theses sp. (Cn) Group F Petraliella bisinuata (Bry) Aplowina Riaantea (Bry) Astropecten duplicatus (Ech) Ctenostomata (Bry) Nolella gigantea (Bry) Reptadeonell tingsae (Bry) Trypsostega a ha: ta (B ry) Scandia mutabilis (Cn) ven. Aplousina gigante@ (Bry) Stephanoscyphus sp. (Cn) Phylactella aviculifera (Bry) Cribrilaria radiata (BrY) Group F Clytia fragilis (Cn) Hippaliosina rostrigera (Bry) Halichondria bowerbanki (PO) Reptadeonella hastingsae (Bry) Ophiothrix angulata (Ech) Sertularia p l!umu.1if (Cn) Spheciospongia vesparium (PO) Schizoporel _Onu::a (Bry) Phylactella aviculifera (Bry) Conopea merrilli (At) Cribrilaria floridana (Bry) Obelia dichotoma (Cn) Homaxinella waltonsmithi (Po) Balanus trigonus (At) Scrupocellaria regularis (Bry) Pilumnus sayi (Ar) Group G Sertularella gayi (Cn) Bellulopora bellula (Bry) Ircinia campana (Po) Dynamena quadridentata (Cn) BuSula rylandi (Bry) Hebella venusta (Cn) Group G Aglaophenia trifida (Cn) Ectopleura dumortieri (Cn) Epizoanthus americanus (Cn) Bugula sp. (Bry) Modiolus americanus (MO) Dynamena cornicina (Cn) Arbacia punctulata (Ech) Cris ia sp. (Bry) Distaplia bermudensis (Ch) Parasmittina nitida (Bry) Tedania ignis (Po) Aglaophenia sp. (Cn) Pteria colymbus (Mo) Celleporaria maznifica (Bry) Eudendrium ramosum (Cn) Petraliella bisinuata (Bry) Ocnus pygmaeus TE-ch) Monostaechas quadridens (Cn) Molgula occidentalis (Ch) Sertularia marginata (Cn) Styela plicata (ChT Bimeria humilis (Cn) Leptogorgia virgulata (Cn) Theses sp. (Cn) Balanus venustus (Ar) Schizoporella floridana (Bry) Parellisina curvirostris (Bry) Group H Group H Poecilosclerida A RO) Microporella umbracula (Bry) Ircinia felix (PO) Astropecten duplican (Ech) Megalobrachium soriat um (At) Dynamena cornicina (Cn) Styela plicata (Ch7- Lophogorgia hebes (Cn) Pteria colymbus (MO) Aplysina fis-tularis (PO) Sertularella conics (Cn) Luidia alternata (Ech) Bugula fulva (BrY7 Cliona caribbaea RO) Aplysina fistularis (Po) Astropecten comptus (Ech) Luidia alternata @Ech) Poecilosclerida B (Fo) Crepidula aculeata (MO) Group I Hemectyon rsei@ (Po) Haliclo-- oculata RO) Kochlorine floridana (Ar) Didemnum c-andidum (Ch) Hippoporina contracta (Bry) Pseudomedaeus agassizii (Ar) Dynamena quadridentata (Cn) Echinaster serpentarius (Ech) Smittina smittiella (Bry) 84 SPECIES GROUPS U) A B C D E F G H I i OS03 OS02 CONSTAN 0S01 MZO.7V@ry High z MS03 IM20.5High 0 MS02 go 10.3 Moderate M ZO. I Low MS01 IS03 C3 < 0. 1 Very Low IS02 IS01 A 8 C-D E F G H I i . . . . . . .. . . . . .. 0:0023 0 FIDELITY 0S01 W.24 Very High z MS03 2023High 0 MS02 2 Moderate NIL. M21 Low MS01 CD < I Very Low :ES03 IS02 ..... ... . . T.S01 Figure 5.9. Inverse classification hierarchies and nodal diagram thowing W., constancy and fidelity of station - species group coincidence based on winter dredqe collections. 85 were fairly ubiquitous in their distribution on the continental shelf, and thus displayed little faithfulness to any station. Species forming groups D and E were most consistently encountered at inner shelf stations but were only moderately faithful there. Groups F and H contained species which were highly constant at both an inner and middle shelf station but were not restricted to either station. Species in group G were very common in col- lectiOnS from MS02 and MS03 but displayed only moderate fidelity to these stations. Species in group I were the most ubiquitous, being consistently encountered at inner, middle, and outer stations. Group J contained species which were also represented at several stations in each depth zone but only displayed high constancy at stations MS02 and OSO3. The inverse cluster analysis of the 101 most frequently occurring species collected in summer dredge sampling yielded 8 species groups (Table 5.11). The nodal constancy and fidelity diagrams (Figure 5.10) indicate that these species assemblages can be described in terms of their constancy and fidelity at inner, middle, and outer shelf live bottom habitats. Those species which were most characteristic of outer shelf stations were found in group A. Species in this group were highly constant and faith- ful to stations OSOI and OS03, although they were highly constant at station MS03, also. None of the species in this group was collected at station OSO2. Species which comprised group B were collected at all outer shelf stations and displayed very high constancy there. Most species in this group, except the bryozoan Cycloperiella rubra. were also collected at either inner or middle stations where they were common at stations MS03 and IS02. The some- what ubiquitous distribution of members of this group is reflected by their moderate to low fidelity values for these stations. Species forming group C were also fairly ubiquitous, although they were most commonly encountered in collections from OSO1. Group D consisted of species which were highly constant at middle shelf stations but were only moderately restricted to them. Species in this group which were collected only at middle shelf stations during summer included the hydroids Hebella venusta, Aglaopheni@ allmani, A. latecarinata, Thyroscyphus marginatus, Synthecium tubitheca, Sertularia.marginata, and Hincksella ' cylindrica; and the bryozoans Chaperia sp. and Nellia tenella. The consti- tuent s-ecies of group E were also common at middle shelf stations and were .P generally much more ubiquitous than any other species group. They were par- ticularly common at stations IS01, IS03, MSOI, MS02, MS03, and OSO1. Species in group H were infrequently encountered at several stations and displayed high constancy only for station MS02. Although some constituent species were fairly ubiquitous, members of groups F and G were primarily characteristic of inner shelf stations. Species in these groups which were collected only at inner shelf stations during summer included the sponge Homaxinella waltonsmithi, the bryozoan Scrupocellaria regularis, the cnidarians Epizoanthus americanus and Eudendrium ramosum, the echinodrems Arbacia punctulata and Ocnus pygmaeus, and the mollusk Modiolus americanus. The seasonal comparison of selected members of species groups is repre- sented by the matrix shown in Figure 5.11. This presentation indicates that most species associations defined by inverse cluster analysis were not con- sistent between winter and slimmer. However, several species did occur together in cluster groups formed by analysis of data collected during both sampling. periods. Notable co-occurrences during both winter and summer sampling, included the ubiquitous bryozoan species Schizoporella cornuta and Reptadeonella hastingsae with the barnacles.Conopea merrilli and Balanus 86 -1A SPECIES GROUPS -0.6- -OA: -0.2- 01 A 8 C D E F G H isol IS02 CONSTANCY 0 IS03 N.Z0.7 Very High z MS01 0 IM20.5High MS02 Q 20.3 Moderate MS03 20.1 Low 0sol M <0.1 Very Low 0soz ............. OS03 A B C 0 E F G H isol IS02 . . . . . . I . . . .FIDELITY IS03 NZ4Very High z MS01 0 E23 High MS02 2 Mod a rate MS03 1 Low 0sol < I Very Low OS02 OS03 Figure 5.10. Inverse classification hierarchies and nodal diagram showing constancy and fidelity of station species group co ncidence based on summer dredge collections. am so "M "*new maww"" M -z' tZ, to to cl C+ 0) Q C+ 0 m C+ C+ QL CD MLnmrD cl CL X 14 f,@- Q: LA C-+ Cz 14 c-+ -I Ln ft "0 0 f4 Q 0 x Z (A =3 Campanuldrid hincksh C+ C+ _0 (a Di :7 V) 0 DInemme cornicifla h < :3 V) (D (0 C+ (D 0 (D 0 Neflostaorchas quqdridotfi.@ 0 Lo 0 0 0 Clyne cylinarica :3 0. l< - C) (A 0 C 0 000100 0 @i-elea anguing 0 V) C: To-chlorine flaridana W c(/) LA C+ -1 0 0) 11 .0 r_ (D -1 0 ot* 0 000 Hippoliosine rostrigera a -1 CD (D -0 (D0 0 rrypsastege venusta - CL 2. rDW 0 . . . . . Microporello cifiola (D CD -5 :3 (D 0 CL CM (n 0) 0 Hippoparina contracle C+ (A @ 0 A A A x PAK I a- :E a) l< Pt PAKI rurbicollepara-WI-chotom vmE3 -(n - . - . . ---A--- S -0 ". LA --AAA Arco zebre 0- Ln (D V) _0 1069 Ob'Olia dichotoma I C) (D 0 0 8010flus vellustus Lo ", ". 0 0 * Clytia frovilis (no- m !D --h m 0CL Ln u, quadridentald CZ it -4 C+ c+ - M:E m 0 *1** Cribrilarid radiate =r M l< 0- Antrepara tincta CL. (a C-+ A CD rn rn (D =r slophanoscyphus SP. 0-h 0 00-1 r) Colloporaria albirostris 0 ritanideum frauenfoldli @ C+ (D 0 - = Roptadsonella hastingsa 0c+ (D M C+ 0= 0 Ircinia campone ct V) crisia 6 P. 0 C:1@ -.0) :3 Ln 0 E3 So/anus trigonas V) -- = (D 0 C+ V) Conopea merrilli -h -3 (D (n 1-3 -h -S schizoporelld cerflufa 0 -% 0 0 c F3 -a 88 trigonus. The bryozoan Crisia sp. and the sponge Ircinia campana, which were also ubiquitous, were classified in the same species group during both seasons. Other winter and summer co-occurrences included the mollusk Arca zebra and the bryozoans Turbicellepora dichotoma, Hippoporina contracta, and Microporella, ciliata. Species Assemblages and Distributional Patterns: Trawl Collections No i 1 analysis of the 42 winter trawl collections produced six station groups (Figure 5.12). Groups 1 and 2 consisted of collections made at inner shelf stations; however, the faunal composition at station IS02 was sufficiently different from that of the other inner shelf stations to justify formation of a separate group. Group 3 consisted of collections from middle shelf stations, and its constituent species were similar to those of three collections from station OS01 (group 4). The other collections from station OS01 formed station group 6. These collections were most similar to others taken at middle shelf stations found in group 5. The formation of totally separate groups (4 and 6) containing collections from the outer shelf was due to their having only two species in common. Similarly, not all collections from middle shelf stations shared the same species. Cluster analysis classified summer trawl collections into four groups (Figure 5.13) which again corresponded, for the most part, to bathymetric location on the continental shelf. Group 1 consisted of collections from OSO1. Groups 2 and 3 largely comprised collections from middle shelf stations; however, two collections from station IS03 were apparently more similar in faunal composition to middle shelf samples than to the other inner shelf from inner shelf stations composed group 4, which was not similar in faunal collections and were also placed in group 3. All of the remaining collections composition to any other station group. Reciprocal averaging ordination of winter trawl collections revealed a more homogeneous zonation pattern across the shelf than did cluster analysis. Axis 1, which accounted for 11.57% of the total eigenvalue, was most successful in separating members of cluster groups 5 and 6 from all other collections (Figure 5.14). These two groups are comprised of middle and outer shelf samples which shared species. Axis 2 explained an additional 8.45% of the total variance. In general, middle and outer shelf stations had intermediate to low scores on axis 2, while inner shelf stations had intermediate to high scores on axis 2. The degree of overlap among members of all cluster groups on axis 2 is considerable, however, suggesting that the faunal assemblages characteristic of each area are more similar to one another than cluster analysis would seem to indicate. The ordination of summer trawl data indicated several misclassifications of collections by cluster analysis. Axis 1, which explained 15.65% of the total variance, successfully separated inner, middle, and outer shelf collec- tions from one another, with the exception of a single middle shelf sample (MS03). This sample appeared to be more similar in faunal composition to trawl collections from the outer shelf than it was to other middle shelf collections (Figure 5.15). This affiliation is not supported, however, by the results of cluster analysis which grouped this collection with other middle shelf samples in site group 3. The ordination results further indicate that two ther collections (both from station IS03) were also misclassified. Thesi samples grouped much more closely in the two dimensional ordination space with members of inner shelf site group 4 than they did with other constituents of site group 3, the group to which these two collections were originally assigned by 89 Trawl.. Station Groups SIMILARITY .8 .6 .4 .2 0 -.2 -4 -.6 Group Station IS03 IS03 IS03 IS03 IS03 IS01 isol IS01 IS01 IS03 IS01 isol IS02 IS02 IS02 IS02 IS02 IS02 MS51 MS03 MS02 MS02 MS02 MS02 3 MS02 MS03 MS03 MS03 MS03 MS01 '601 - - - 4 OSO1 ------- OSO1 MS02 MS01 MS01 5 MS01 MS03 MSO I WTI 6 OSO1 OSO1 .8 .6 .4 .2 0 -2 -.4 -.6 SIMILARITY Figure 5.12. Normal cluster dendrogram of winter trawl collections indicating station groups formed using the Jaccard similarity coefficient and flexible sorting. 90 Trawl: Station Groups SIMILARITY 7 .5 Group Station osol osol osol osol osol osol - - - a-sor- MS02 MS02 MS02 MSO I MSO I : Sol Sol asof- MS03 1503 IS03 MS03 MS03 M803 MS02 M803 MSO1 noLr- IS02 ISO[ IS02 IS02 IS02 4 1301 IS02 1501 IS03 IS03 IS03 IS03 1301 Isol r r---r .7 .5 3 SIMILARITY Figure 5.13. Normal cluster dendrogram of summer trawl collections indicating station groups formed using the Jaccard similarity coefficient and flexible sorting. MM" " W " " M "" IMAM aw Mso 100, 0' 3: SO 1 ISOI -CD 01SOI Cluster 90- ISO10 MSOI Groups ISO10 0IS01 0 80- OIS02 4 a 70- OIS02 5 0 0 IS02 8 MSO, OIS03 IS03 6 0 60- OIS03 6 MS02 U) IS03 00:ESO3 OIS03 50- ISO2* A OSO1 0 M 0 MS01 SOZ 40- 0IS02 16 MSO'3 ,AOSO 6MSO26MSOI 30- OIS02 MSOi 6,amsu 0 MS01 NOSO1 20-A NMS02 OSOI 6 MS03 6 MS03 10- 6MS93 6 MS03 0SO1 MS01 0 Ti 0SO1 C)MS03 0 1 T--------T 1'0 20 30 40 50 @O -rO 80 90 160 AXIS I Figure 5.14. Results of reciprocal averaging ordination showing orientation of winter trawl collections at stations on axes I and 2. Symbols indicate which group these collections were placed into by cluster analysis. 100- 0IS03, Cluster 90- A IS02 Groups A IS03 MS020 OMS02 0 so- ISO1 OMS02 0 A AISOI OMSOI 3 a A ISM 6IS03 6 MS03 0 MSOI 4 a To- AIS01 ,Sol AISOZ MS036 6MS03 MSO1,5 A& T-SO 2 0 60-IS03A AIS02 0 MS01 N IS01 MS02 50- A-TsO3 A IS03 6MS02 0 6MS026 AIS03 MS01 MS03 %0 X 40- 00S01 30- 00sol OSO106M 00S01 S03 20- 00SO1 10- nosof 0 10 20 30 @O @O 6'0 TO 80 90 10,0 AXIS I Figure 5.15. Results of reciprocal averaging ordination showing orientation of summer trawl collections at stations on axes 1 and 2. Symbols indicate which group these collections were placed into by cluster analysis. aw kin so so 40 to aw, 06 00 MW '00 $0 'ON M 411110 as 93 cluster analysis. Axis 2 explained 8.26% of the total eigenvalue and separated outer shelf collections (site group 1) from inner (group 4) and middle shelf (groups 2 and 3) collections. Some degree of separation existed between the two groups of middle shelf samples along axis 2, but not enough to warrant their being considered representative of very different habitat types. Nine groups were formed by inverse analysis of the 107 species remaining after reduction of winter trawl data (Table 5.12). The nodal diagram indicates that group A is comprised of an outer shelf assemblage of species which were not very common at any station and were generally restricted to station OS01 (Figure 5.16). As indicated by the cluster hierarchy, species in this group bore little resemblance to members of other groups in terms of their distribu- tion. Species in group B were characteristic of the inner shelf live bottom habitat, where they were consistently collected at all stations. Although several species in this group were infrequently collected at middle shelf stations MS02 and MS03, the tunicate Clavelina picta, the sponge Homaxinella waltonsmithi, and the octocoral Leptogorgia virgulata were only collected on the inner shelf. Species in groups C and F were also found on the inner shelf where they displayed moderate constancy and high fidelity for stations IS01 and IS02, respectively. Although groups D and E contained species which were somewhat ubiquitous, many such as the echinoderms Lytechinus variegatus and Ocnuspygmaeus, the tunicates Diplosoma macdonaldi and Pyura vittata, and the mollusk Diodora cavenensis were collected only at inner shelf stations. These and ot-her species in the two groups were particularly constant in collections at IS02 where they also displayed moderate to high fidelity. Groups G, H, and I contained relatively rare species which were not very constant or very faithful at any station. These species displayed their maximum constancy and fidelity at inner and middle shelf stations. As with the winter trawl data, classification of 113 species from summer collections produced groups which were generally identifiable with live bottom habitats of the inner, middle, and outer continental shelf (Table 5.12 and Figure 5.17). Species in group A were characteristic of the middle shelf live bottom habitat where they were consistently collected and moderately restricted to stations MS01 and MS02. Group B species were fairly ubiquitous but not particularly common or highly faithful among collections at any given station. Species which were restricted to and highly constant in collections from station OS01 formed group C. These included the scyphozoan Stephanocyphus sp., the hydroids Dynamena dalmasi and Sertularella areyi, the octocoral Telesto sanguinea, the barnacle Scalpellum diceratum, the decapods Pachycheles rugimanus and Euchirograpsus americanus, the ascidian Didemnum sp. A, and the e@hl-inoderm Astroporpa annulata. Those in group D were also consistently collected at OS01 and were fairly ubiquitous although not as commonly found at other stations on the shelf. Group E species occurred in collections from inner, middle,and outer shelf live bottom habitats but were not common at any station. Species which formed group F were collected at inner and middle shelf live bottom habitats, but they were not particularly constant or faithful in collections from either area. Species in group G were ubiquitous among inner shelf stations but were most frequently collected at station IS02. As indicated by the dendrogram hierarchy of Figure 5.17, assemblages of groups F and G did not resemble those of other species groups. The composition of most invertebrate assemblages defined by cluster analysis of trawl data changed from one sampling period to the next (Figure 5.18); 94 Table 5.12. Species groups resulting from numerical classification of data from samples collected by trawl during winter and summer, 1980. (Ar - Arthropods; Bry - Bryozoa; Ch - Chordata; Cn - Cnidaria; Ech - Echinodermata; Mo Molluscs; Po - Porifera). I I Winter 1980 Summer 1980 Group A Group A Aglaophenia elongata (Cn) Hebella venusta (Cn) Dynamena dalmasi (Cn) Chaperia sp. (Bry) Cyanea capillata (Cn) Aeverrillia setigera (Bry) Renilla reniformis (Cn) Aglaophenia trifida (Cn) Mesopenaeus tropicalis (Ar) Scandia mut@-bilis (Cn) Solenocera atlantidis (Ar) Aglaophenia latecarinata (Cn) Metapenaeopsis goodei (Ar) Bimeria humilis (Cn), Sicyonia brevirostris (Ar) Crisis sp. (Bry) Thyroscyphus marainatus (Cn) Group B Clavelina gigantea (Ch) Schizoporella floridana (Bry) Clavelina picta (?) (Ch) Aglaophenia allmani Cn) Homaxinella waltonsmithi (Po) Styela plicata (Ch) Group B Leptogorgia virgulata (Cn) Lophogorgia hebes (Cn) Hebella scandens (Cn) Spheciospongia vesparium (Po) Amathia distans (Bry) Synalpheus longicarpus (Ar) Buitula rylandi (Bry) Penaeus duorarum (Ar) Synthecium tubitheca (Cn) Trachypenaeus constrictus (Ar) Aetea anguina (Bry) Campanularia hincksii (Cn) Group C Nellia tenella (Bry) Sertularia marginata (Cn) Oculina arbuscula (Cn) Celleporina hassalli (Bry) Asterias sp. A (Ech) Clytia @i-li@s-FCn-) Tozeuma serratum (Ar) Dynamena guadridentata (Cn) Rossia tenera (MO) Amathia a lt e .ta (Bry) Aglaophenia rigida (Cn) Titanideum frauenfeldii (Cn) Sertularella conica (Cn) Hadromerida B kPo) Group C Megalobrachium soriatum (Ar) Haliclonidae B (PO) Clytia cylindrica (Cn) Sertularia marginata (Cn) Celleporaria magnifica (Bry) I-n-aroucium stellatum (Ch) Scalpellum diceratum (At) Pandaros acathifolium (Po) Sertularella areyi (Cn) Dynamena cornicina (Cn) Rochlorine floridana (Ar) Dromidia antillensis (Ar) Filellum serratum (Cn) Cinachyra alloclada (Po) Pachycheles ruRimanus (Ar) octopus sp. (MO) Telesto sanguinea (Cn) Pseudomedaeus agassizii (Ar) Group D Ealathea rostrata (Ar) Nolella Rigantea (Bry) Turbicellepora dichotoma. (Bry) Dynamena dalmasi (Cn) Antropora tincta (Bry) Keratosa D (PO) Balanus trigonus (At) Didemnum sp. A (Ch) Balanus venustus (Ar) Sertularella (Cn) Lytechinus variegatus (Ech) Synalpheus tournsendi (Ar) Pilumnus pannosus (Ar) Xytopsues griseus (PO) Ocnus pymaeus (Ech) Sizmadocia caerula (PO) Mithrax pleuracanthus (Ar) AStroporpa annulata (Ech) Diplosoma macdonaldi (Ch) Euchirograpsus americanus (Ar) Diodora cayenensis (Mo) S ephanoscyphus-;,P- @(C Conopea galeata (Ar) Hippoporina contracts (Bry) Group D Clytia cylindrica (Cn) Microporella ciliata (Bry) 95 Table 5.1.2 (Continued) Winter 1980 Summer 1980 Group E Balanus trigonus (Ar) Conopea merrilli (Ar) Microporella ciliata (Bry) Turbicellepora dichotoma (Bry) Crisia sp. (Bry) Schizoporelia cornuta (Bry) Monostaechas quadridens (Cn) Sicyonia brevirostris (At) Ophiothrix angulata (Ech) Solenocera atlantidis (Ar) Arbacia punctulata (Ech) Astrophyton muricatum (Ech) Epizoanthus americanus (Cn) Celleporaria albirostris (Bry) Telesto fruticulosa (Cn) Metapenaeopsis goodei (Ar) Pyura vittata (Ch) Petraliella bisinuata (Bry) Titanideum, frauenfeldii (Cn) Group F Group E Diplosoma macdonaldi (Ch) Kochlorine floridana (Ar) Didemnumi candidum (Ch) Ircinia felix (Po) Pilumnus floridanus (Ar) Bugula grayi (Bry) Obelia dichotoma. (Cn) Scrupocellaria regularis (Bry) Cinachyra ku thali (PO) Celleporaria magnifica (Bry) Cliona caribbea (P-0 ) Eucidaris tribuloides (Ech) Group G Stylopoma informata (Bry) Stenocionops furcata coelata (Ar) Ircinia ramosa (Po) Eudendrium tenell= (Cn) Aeverrillia setigera (Bry) Synalpheus longicarpus (Ar) 7s-trophyton muricatum, (Ech) Aplysina fistularis (PO) Aplysina fistulaTl7s-(Po) Paguristes tortugae (Ar) Dynamena quadridentata (Cn) Ircinia strobilina. (Po) Stenocionops furcata coelata (Ar) Scyllarides nodifer (Ar) Sertularella pinnigera (Cn) Group H Ircinia campana (Po) Hippaliosina rostrigera (Bry) Ircinia campana. (Po) Aplousina gigantea (Bry) Hemectyon pearsei (Po) Hippoporina contracts (Bry) Poecilosclerida A (Po) Ctenostomiata (Bry) Haliclona oculata (Po) Stomolahus meleaaris (Cn) Echinaster sp. (Ech) Holothuria princeps (Ech) Tamoya haplonema (Cn) Keratosa C (P.) Pilumnus savi (Ar) Pteria colymbus (Mo) Group F Synalpheus townsendi (Ar) Cliona caribbaea (Po) Penaeus duorarum (Ar) Synalpheus minus (Ar) Epizoanthus americanus (Cn) Pseudomedaeus agassizii (Ar) Turritopsis nutricula (Cn) Cinachyra keukenthali (Po) Symplegma. vi-ri-d-e--T-Ch) Ircinia strobilina (Po) Trachypenaeus constrictus (Ar) Portunus gibbesii FAT T Group I Conopea galeata (Ar) Antropora tincta (Bry) Nellia tenella (Bry) Ciocalapata gibbsi (Po) Bugula fulva (Bry) Sertularella conica (Cn) Amathia distans (Bry) HI-avelina gigantea (Ch) Group G Aglaophenia trifida (Cn) Scandia mutabilis (Cn) Pilumnus sayi (Ar) Obelia dichotoma (Cn) Dromidia antillensis (Ar) Clytia fragilis (Cn) Aplidium, constellatum (Ch) Sertularia plumulifera (Cn) Diodora cayenensis (MO) Campanularia hincksii (Cn) Mithrax pleuracanthus (At) Pilumnus; floridanus (Ar) Ocnus pygmaeus (Ech5 Filumnus dasypodus (Ar) i@'I-anus venustus (Ar) Pagurus carolinensis (Ar) Homaxinella waltonsmithi (Po) Celleporaria albirostris (Bry) Synalpheus minus (Ar) - Bugula rylandi (Bry) Molgula .'. c identalis (Ch) Schizoporella cornuta (Bry) Styela plicata (Ch) 96 Table 5.12 (Continued) Winter 1980 S,,@er 1980 Ectopleura dumortieri (Cn) Leptogorgia virgulata (Cn) Nolella gigantea (Bry) Spheciospongia vesparium (Po) Cla@h-rina coriacea (Po) Halocordyle disticha (Cn) Aglaophenia sp. (Cn) Lophogorgia hebes (Cn) Hebella venusta (Cn) Distaplia bermudensis (Ch) Schizopo@-rella floridana (Bry) Haliclona oculata (Po) Thyroscyphus marginatus (Cn) Pteria colymbus (MO) Hebella scandens (Cn) ArbWc-la punctulata (Ech) Conopea merrilli (Ar) Ophiothrix angulata (Ech) Muricea pendula (Cn) Dynamena cornicina (Cn) Turritopsis nutricula (Cn) Monostaechas quadridenS (Cn) 97 SPECIES GROUPS t -0.3 -0.11 1 1 A B C D E FG H I 0S01 MS03 CONSTANCY EZOIVery High MS02 z 0 13Z0.5High MS01 EB20.3 Moderate IS03 M10. I Low IS02 < 0. 1 Very Low ISO I A 8 C D E FG H 0S01 11 MS03 FIDELITY E24 Very High Z MS02 1jz3 High MS01 R. EgZ2 Moderate T.SO 3 EMZILow IS02 < I Very Low T.So I . . . . . . . . . . Figure 5.16. Inverse classification hierarchies and nodal diagram showing constancy and fidelity of station - species group coincidence based on winter trawl collections. 98 SPECIES GROUPS -1.4 -12: -1.0 -0.8: -,OL6- -OA- - -2-- 00: A S c D E F 6 IS01 CONSTANCY ISM M20.7Very High z IS03 1020.5 High 0 MS01 Q20.3 Moderate MS02 M20. I Low MS03 r7l <0. I Very Low OSOI . . . . . . . . . . . . . . . . . . . . . . . . A 8 C D E F G IS01 .......... ...... FIDELITY IS02 M24 Very High U) . ..- - -- - I z IS03 IM23 High 0 MS01 gg Z2 moderate P- MS02 M21LOw Ms 3 r7l <I Very Low 0sol Figure 5.17. Inverse classification hierarchies and nodal diagram showing constancy and fidelity of station - species group coincidence based on summer trawl collections. 99 -Z 1L CL to a mz Ilk Z lei Zj It Nobel/& reftusto 0 Agloophooriv trifiale I 4d I Of* 4P 191*1 1 1 1 40 1 *1010101 1 1 ho#*$ riffulalff, !@WP Plics Hooffqzl@r#/Ap walfonsm,thi A-we distafts 0 obelid dicAofame Olwo E@L@ fmidis -M Ole Cone lbirostris I I I Moe?/"/ Arorimstris rildowdleum fro"fifeldii re/0810 frMficulose Chypef/ so. off/eflus frig0flu Claw/00 'll'off jadu to. micropor#110 elliato WINTER Alyfidiv constellefum mo/opu *e4rdefifells SUM MER me dlistlehe 0410,01iff Permudeftsis WINTER 6 SUMMER Ar .1. unctulara 100chas gaverldelps 'Voliclofte OCY/0'a Olotolo All/umovs Rev Col'iffstor sp. B 91*10 ramolo Aff.010Irma 010 syoo/phous townsefidt 0 F/1-000 ed,166000 ro'bicellf'odre d'ehotome L AStrophjfoa muricatum Fiaure 5.18. Matrix showing co-occurrence of species within the same group formed by inverse cluster analysis of trawl collections from winter sampling only, summer sampling only, or both winter and summer sampling. Species were selected for inclusion in the natrix if they occurred at > 50% of the collections from at least 2 stations sampled by frawl. 100 however, several recurrent groups of species did occur. The bryozoan Schizoporella floridana; the tunicate Clavelina gigantea; and the cnidarians Thyroscyphus marginatus, Aglaophenia trifida, and Hebella venusta formed a cohesive middle shelf species assemblage during both winter and summer. These species were part of a group which displayed moderate constancy and fidelity forf.tat ion MS02 in winter, and were quite common at stations MS01 and MS02 in er. The cnidarian Clytia fragilis and the bryozoan Amathia distans co- curred with the aforementioned recurrent group in winter samples but were part of a separate group of fairly ubiquitous but uncommon species in the -sinmer. The bryozoans Schizoporella cornuta and Celleporaria albirostris; and the barnacle Conopea merrilli were also classified in the same group during both seasons. In winter, these species were part of an assemblage that was not very constant or faithful at any station, while in summer, they were classified with species which were ubiquitous yet most frequent at OSO1. A consistently co-occurring group of species from the inner shelf stations included the sponges Spheciospongia vesparium and Homaxinella waltonsmithi, the cnidarians Lophogorgia hebes and Leptogorgia virgulata, and the tunicate Styela Rlicata. The hydroid Monostaechas quadridens and the echinoderms .Ophiothrix angulata and Arbacia punctulata formed another assemblage which was frequently encounted on the inner shelf at station ISO2. The mollusk Pteria colymbus, the sponge Haliclona oculata, and the decapod Pilumnus sayi clustered together during winter and summer. They occurred with species which were not common but which were ubiquitous at inner and middle shelf stations in winter. During summer they clustered with species which frequently occurred in inner shelf collections. Quantitative Assessment of Benthos Captured by Suction and Grab Samplers: Species Composition and Abundance - A total of 813 identifiable taxa were collected with suction and grab samplers during winter and summer. This total excludes cnidarian and bryozoan taxa which were not examined. A listing of all taxa collected and ranked by abundance at each station, along with density estimates for each taxon, is presented in Appendices 10 and 11. The phylum Annelida was represented by the greatest number (261) of recognizable species. Annelids also dominated collections in terms of numerical abundance, accounting for '@., 64.7% of the total of 38,325 inverteorates collected. Mollusca ranked second among the invertebrate phyla with a total of 203 recognizable species; however, with respect to abundance, mollusks accounted for only 4.1% of the total number of individuals. Other groups with fewer numbers of species were Decapoda (97 taxa), Amphipoda (82 taxa), Porifera (61 taxa), other Crustacea (39 taxa), Echinodermata (30 taxa), Ascidacea. (15 taxa), Pycnogonida (11 taxa), Sipunculida (8 taxa), and Nemertinea (6 taxa). The phylum Amphipoda was the second most abundant group and comprised r@u 17.4% of the total number of invertebrates collected. Macroalgae were collected during our sampling with suction and grab; however, in most instances, only small fragments were collected, and these were generally damaged, making identification impossible. Algae occurred in 11 of the samples collected during winter and in 28 samples collected during summer. The only identifiable taxon collected was Ulva sp. 4hich was -present in two collections taken by Smith-McIntyre grab during winter. The ten numerically dominant invertebrate species from all stations for 101 both sampling periods were the polychaete Filograna implexa (n = 14,914), Phyllo haetopterus socialis (n = 2264), Spiophanes bombyx (n = 751), Exogone dispar (n = 686), and Syllis spongicola (n = 494); the amphipods Photis sp. (n = 647), Podocerus sp. (n = 543),.Luconacia incerta (n = 505), and Erichtbonius sp. A (n = 492); and the echinoderm Ophiothrix.angulata (n = 428). These species accounted for ru 56.7% of the entire invertebrate catch from combined winter and slimmer samples. The ranking of these numerically dominant species changed considerably from winter to summer, with the exception of the colonial serpulid polychaete Filograna implexa which greatly outnumbered all other invertebrates during both sampling-periods (Table 5.13). Differences also existed in dominance between bathymetric zones of the inner, middle, and outer shelf stations (Appendices 10 and 11). Inner shelf stations were dominated in winter by the polychaete Exogone dis_par; the amphipods Luconacia incerta, Lembos smithi and Photis sp.; and the echinoderm Ophiothrix angulata. In summer, the polychaete Filograna, implexa. and the amphipod Ampelisca agassizi constituted a major part of the inner shelf samples. Filograna implexa had the highest density nu 788 individuals per 0.10 mZ at station ISO2. Filograna implexa. was overwhelmingly dominant at middle shelf stations during 'both winter and summer. The maximum winter density for this species was 1197 individuals per 0.10 m2 at station MS01; however, this was the only middle shelf station at which it was abundant. Maximum density of F. implexa. was lower during summer (1%, 424 individuals per 0.10 m2), and once again the species was most abundant at station MS01. Other dominant winter species from the middle shelf included the polychaete Sabellaria vulgaris vulgaris and the amphipods, Photis sp., Caprella. penantis, and Luconacia incerta. Syllis spongicDla was abundant in summer collections from middle shelf live bottom habitats. No species was overwhelmingly dominant in winter at outer shelf stations. In fact, winter collections from the outer shelf were unique in that no species was represented by more than 50 individuals at a station. Consequently, average densities of species did not exceed 10 individuals per 0.10 m2. This may reflect decreased collecting efficiency by the grab sampler on hard substrates. During summer, Filograna implexa and PhXllochaetopterus socialis accounted for most of the invertebrates collected. These species had respective densities of 733 and 442 individuals per 0.10 m2 at station OSO3. Spiophanes bombvx and Erichthonius sp. A were also important at outer shelf stations, although their abundance was considerably less than F. implexa and P. socialis. Abundances, expressed as the arithmetic mean of the logarithmically transformed counts, of each of the ten numerically dominant species are shown in Figures 5.19 - 5.28. Filograna implexa was most abundant at stations on the middle shelf, although large numbers of this species were also collected at station OS03 (Figure 5.19). Winter and summer abundances of F. implexa. for data from all stations were not significantly different (P > 0.05, Mann-Whitney U-test), and we observed no apparent latitudinal trends in abundance. This species occurred in 12% of the suction and grab collections taken during winter and in 31% of those taken during simmer. Phyllochaetopterus socialis, another colonial polychaete, was most abundant at stat1ons IS01 and OS03 (Figure 5.20). There were no significant differences (P > 0.05, Mann-Whitney U-test) in abundance between winter and summer collections, although it is noteworthy that P. socialis was collected only at inner shelf stations where it occurred in only 12% of the winter suction samples and 25% of the summer suction and grab samples. No latitudinal Table 5.13. Numerical ranking of invertebrate species collected by auction and grab samplers. Listing includes only those species represented by >20 individuals. Percents are based on total invertebrate abundance for winter and summer separately. Numerical dominants are Indicated by M. WINTER SUM14ER Total Percent Total Percent Species Number of Total Species Number of Total *Filograna implexa 4818 28.14 *Filoitrana implexa 10,096 47.70 *Exogone dispar 631 3.69 *Phyllochaetopterus socialis 2227 10.52 @Photis op. 552 3.22 *Spiophanes bombyx 583 2.75 *Podocerus op. 520 3.04 *Erlchthontus op. A 464 2.19 *Luconacia incerta 445 2.60 *Syllis spongicola 366 1.79 Erichthonius brasiliensis 358 2.09 Chevalia op. 241 1.14 *Ophiothrix angulata 333 1.94 Protomedia op. 212 1.00 Lembos smithi 265 1.55 Ampelloca agassizi 200 0.94 Aspidosiphon spinalls 247 1.44 Melita appendiculata 176 0.83 Caprellidae A 235 1.37 Aspidosiphon spinalis 130 0.61 Ampelisca agassizi 207 1.21 Sabellidae B 120 0.57 Sabellaria vulgaris vulgaris 204 1.19 *Ophiothrix angulata 95 0.45 Caprella penantis 184 1.07 *Photis sp. 95 0.45 Oxyurostylis smithi 182 1.06 Amphipoda E 91 0.43 *Spiophanes bombyx 168 0.98 Pista palmata 88 0.42 Ampharete americans 163 0.95 @n-ciola laminosa 87 0.41 0 Owenta fusiformis 161 0.94 Acanthohaustorius millsi 81 0.38 Nelita appendiculata 157 0.92 Amphlodia pulchella 79 0.37 Medlomastus californiensis 146 0.85 Ampelisca vadorum 74 0.35 Amphiodia pulchella 138 0.81 Chone americans 70 0.33 *Syllis spongleola 128 0.75 Pagurus hendersoni 61 0.29 Tanaidacea A 126 0.74 *Luconacia incerta 60 0.28 Sabellaria vulgarts beaufortensis 123 0.72 *Exogone dispar 55 0.26 Lumbrineris inflata 116 0.68 Tellina americans 54 0.26 Carpias bermudensis 116 0.68 Gammaropsis op. 54 0.26 Megalobrachium soriatum 115 0.67 Lumbrineris coccinea 53 0.25 Ampelisca vadorum 109 0.64 Spio pettiboneae 53 0.25 Polycirrus carolinensis 93 0.54 Onuphis nebulosa 51 0.24 Prionosplo cristata 91 0.53 Lumbrineris inflata 51 0.24 Chrysopetalidae A 88 0.51 Owenia fustformis 50 0.24 Syllis gracilis 88 0.51 Chrysopetalidae A 50 0.24 Plata palmata 84 0.49 Pagurus carolinensis 50 0.24 Elasmopus op. A 81 0.47 Lembos smithi 49 0.23 Lembos unicornis 79 0.46 Axiothella mucosa 48 0.23 Web IQ Eta tridentata 77 0.45 Megalobrachium soriatum 47 0.22 Lo,mrmef M usa 73 0.43 Harmothoe op. A 46 0.22 hyall a 69 0.40 Amphipoda G 46 0.22 Unciola laminosa 65 0.38 Nassarius albus 42 0.20 Gammaropois.9p. 57 0.33 Crassinella lunulata 41 0.19 Paracerceis caudata 57 0.33 Scypha barbadensis 41 0.19 Sipunculida A 54 0.32 Eunice vittata 40 0.19 Phtisica marina 53 0.31 Megalowma bioculatum 38 0.18 So we so as of Ow M M as M an so " Table 5.13 (Continued) WINTER SUMER Total Percent Total Percent Species Number of Total sReclas Number of Total Eulalia sanguinea 53 0.31 Nicomache trispinata 38 0.18 Eunice vittata 53 0.31 Amphioplus op. 38 0.18 Pagurus carolinensis 53 0.31 Paraprionosplo pinnata 36 0.17 Ampithoe op. A 48 0.28 Craniellidae, B 36 0.17 Elasmospus op. B 47 0.27 Syllis hyalina 35 0.17 Mitrella lunata 45 0.26 Ampharete acutifrons 35 0.17 Axiothella mucosa 45 0.26 Phyllodoce longipes 34 0.16 Autolytus op. 44 0.26 Onuphis pallidula 33 0.16 Ampelloca op. B 44 0.26 Eulalla sanguinea 33 0.16 Pista quadrilobata 43 0.25 Gouldia cerina 33 0.16 Glycera tesselata 41 0.24 Varicorbula operculata 32 0.15 Sicyonia laevigata 40 0.23 Laonice cirrata 32 0.15 Amphipoda A 39 0.23 Elasmopus op. A 32 0.15 Pherusa inflata 39 0.23 Lemboo unicornis 32 0.15 *Phyllochaetopterus socialis 37 0.22 Lysianopois alba 31 0.15 Phyllodoce fragills 36 0.21 Goniadides carolinae 31 0.15 Chone americana 35 0.20 Polycirrus carolinensis 30 0.14 Syllidae A 34 0.20 Ophiostigms op. 30 0.14 0 Latreutes parvulus 34 0.20 Ophiophragmus op. 30 0.14 W Odontosyllis fulgurans 33 0.19 Ampelisca op. B 30 0.14 Haera op. A 32 0.19 Trichophoxua floridanus 30 0.14 Acanthohaustorius shoemakeri 32 0.19 Alpheus normanni 30 0.14 Euceramus praelongus 32 0.19 Laevicardium pictum 29 0.14 Anachis hotessieriana 31 0.18 Melitidae A 29 0.14 Prtonospio cirrifera 31 0.18 Glycera op. B 29 0.14 Crepidula aculeata 30 0.18 Spiophanes op. A 28 0.13 Lysianopsis alba 30 0.18 Stenopleustes op. A 28 0.13 Microdeutopus myerai 29 0.17 Tanaidacea A 28 0.13 Pherusa ehlersi 29 0.17 Nassarina minor 27 0.13 *Erichthonius op. A 28 0.16 Stpunculida A 26 0.12 Eulalia macroceros 28 0.16 Prionospio op. B 26 0.12 Crassinella lunulata, 28 0.16 Prionospio cristata 26 0.12 Pagurus hendersoni 28 0.16 Ceratonereia mirabilis 25 0.12 Polydora tetrabranchia 27 0.16 Pilumnus floridanus 25 0.12 Syllis alternata 27 0.16 Clathrina coriacea 25 0.12 Laonice cirrata 27 0.16 Chondrilla nucula 24 0.11 Nicomache triapinata 26 0.15 Unciola op. A 24 0.11 Podarke obscura 25 0.15 Notomastus americanus 24 0.11 Pelia mutica 25 0.15 Websterinereis op. A 23 0.11 Cerapus tubularis 24 0.14 Plata quadrilobata 23 0.11 Leucothoe spinicarpa 24 0.14 -Fj@oplodactylus petiolatus 23 0.11 Ophiostigma isacanthum 24 0.14 *Podocerus op. 23 0.11 Cinachyra kuekenthali 22 0.13 Bowmantella portoricensis 23 0.11 Paguristes tortugae 21 0.12 Phyllocarida 22 0.10 Table 5.13 (Continued) WINTER SUMMER Total Percent Total Percent Species Number of Total Species Number of Total Botula fusca 21 0.12 Pseudeurythoe ambigua 22 0.10 Phyllodoce longipes 21 0.12 Leucothoe spinicarpa 21 0.10 Spio pettiboneae 21 0.12 Runida irrasa 21 0.10 Streblosoma sp. 21 0.12 Synalpheus townsendi 21 0.10 Onuphis nebulosa 21 0.12 Malacoceros glutaeus 21 0.12 105 34* 800 South C cc rr oo 11 i nn a Filogran imp W z 4.0- z3.0- 2.0- U. W Z x 0 W 0.01L number of n occurrences -CHARLESTON". number of samples 0 lift- 01SOI 32* S AVA N N .2 .2 i 5. 5 *MS01 "OS01 820 OMS02 Georgia 320 :J .2.2 00SO2 IS02 5 BRUN IdK MS03 5 OOSO5 OIS03 JACKSONVILLEL. V Boo .7- Figure 5.19. Relative abundance of Filograna implexa during winter and summer, 1980. -n C) :11- T. W C+ m IMP 40 c- c CID 0) v) z =3 z Z: 0 z < A.: 0 =r r 0 0 V-01 - cn Z =r U) lw C+ 14W l(Alo Italo 0 rio M-i 0 0 0 zlz INDEX OF ABUNDANCE p to L. CD TER s-.- N, m Eft C+ rD -n (D CD 4A ;a to c (D C+ < 0 w (D % C- 03 cr z I> ;K CL z 0 CD 0 r m Z.. 0 U) 'a =r (D tn CAI& 0 U) Is- CL c ; 0, *0- ch Z= INDEX OF ABUNDA 0 rv 0 to to (A b 0 b b c or It CID S3 03 WINTER 0, SUMMER C+ CL 108 34* so* South Carolina Exogon dispa W 5JD- 4.0 Z D ....... LA. 2.0- M: 61 x W 0 Z 0 number of n occurrences 7u- 0 -.-CHARLEST mber of samples IL elsol 4 4 4 s VANN 'H .2 k 5,5 OMSOI OOSOI 820 MS02 Georgia 320 .22. 5.5 *OS02 IS02 5 a UNSWICK 5 0 ]1k L5 OMS03 5 OOSO3 3:SO3 JACKSONVILLE Sze 800 Figure 5.22. Relative abundance of Exogone dispar during winter and surmer, 1980. 109 34* so* South Carolina Syllis spongicold Z4.0 3.0- 2.0- Lu 0 1.0- x W Ma 00.0- number of occurrences -CHARLE STON.'- N number of samples 12 z eisol 32*-` 5 5 S VANN H. 0 0 OMSOI 4 00S01 82* *MSO2 Georgia 2 1 @<32* OIS02 1 00SO2 BRUNS ICK 5 MS03 Ac OS03 OIS03 JACKSONVILLE".. so* I L Figure 5.23. Relative abundance of Syllis spongicola during winter and summer, 1980. -n m Ln @a 4@b CD-- to C+ Iw C- 0 z z E : : CL 0) z (D r 0 Y- rn rn =r 0 C+ El) 0 0 10 (A 0 U) CL r-. ; cn 0 U) p 0 ca to :E U) Zj= C+ INDEX OF ABUN m 0 0* co C= oc 1 101 1bi 1 61 1 3 a 23 9 WINTER CL SUMMER to IT) to 00 340 800 South Carolina Podocerus sp. 5.0- 4.0- --34* J.:. 2 M L& 2.0 Ir 0 x z a Uj 00 numberof occuffences CH A R LESTON' N number of samples OISOI 4 0 S VANNAH MWI 5 OOSOI PO 5 OMS02 Georg 320 1 ILa5 @.IS02 OOS02 5 BRUN ICK'i: OMS03 OOS03 OIS03 JACKSONVILLE so* Figure 5.25. Relative abundance of Podocerus sp. during winter and summer, 1980. ev ul /V C rD I'D c+ IMP I'D 0 co 0- 0 z 0 < CL 0 z r Ito m Itp 0 (1) cn Its C) is (Alto (D V+ L.Li CL o (00 Ito 0 U) ZI INDEX OF A 0 0 0 BUNDANC U3 (A f\) !4 0 0 0 r 3 3 X _-o WINTER 0 SUMMER 00 0 C+ CAP m "ap. CL 113 340 800 South Carolina Erichlbonius sp. A 4.0- 3 4 2 3.0- 2-0- W x 1.0 Lu 001h number of occurrence ....CHARLESTO N number of samples 5.5 OISOI 320 3 4 15 5 S VANN 4.5 0 0 IL Msol 820 0 OOSOI MS02 Georgia 3 <320 5 :@5 5.5 OS02 OIS02 4 B UNSWIdK 0 0 - T OMS03 - @-15 5.5 OOS03 OIS03 JAC KSONVILLE 820 800 Figure 5.27. Relative abundance of Erichthonius sp. A during winter and summer, 1980. F1 -n -8. m 03 ::I, P. (A m 19 (D rt. 0 (D @j ;a 7D ol 00 0 z N z CL tn 0 Z m 0 m rn C) 0 0 C+ Pi 0 ICA Jb 00 0 U) 0 0 Lo 04 4 0 C+ 0 plo cn U) 0 0 0 zl- INDEX OF ABUNDANC N 0 7- N to ab 6 o b b b CID WINTER 3K SUMMER :E Ld C+ CL 115 differences in abundance were noticed. The infaunal tube building spionid polychaete Spiophanes bombyx was collected at every station during our study. It occurred in 65% of the suction and grab samples in winter and 51% in summer. Abundances were greatest at stations OS01 and OS02 during summer when S. bombyX was collected in all samples at both stations (Figure 5.21). No significant difference between winter and summer abundances of S. bombyx was found (P > 0.05, Mann-Whitney U-test). .@@:ogone dispar, a syllid polychaete, was most abundant at inner shelf sta- tions (Figure 5.22). This species was also collected at stations on the middle shelf but was not found at outer shelf localities. It occurred in 51% of all winter suction and grab collections and 20% of the summer collections. There was no significant difference in the abundance of E. dispar between winter and summer sampling periods (P > 0.05, Mann-Whitney U-test), even though the species was collected at twice as many stations during the winter. Another syllid polychaete, Syllis spongicola, was collected at every station. in both seasons (Figure 5.23). It was most frequently encountered in summer when it occurred in 44% of the suction and grab samples. In winter, it was present in 42% of the collections. It was most abundant at stations MS01 and MS03, and least abundant at outer shelf stations. Abundances were not significantly different between winter and summer (P > 0.05, Mann-Whitney U-test). The amphipod Photis sp. was most abundant at inner and middle shelf stations where it was collected almost exclusively during winter (Figure 5.24). It was collected in 74% of the winter suction and grab collections and in 31% of the summer collections. At outer shelf stations, Photis SP. was most abundant in summer; however, no significant difference was noted in the overall abundance of Photis sp. between sampling periods (P > 0.05, Mann-Whitney U-test). Podocerus sp. was ubiquitous on the continental shelf; however, its abundance was greatest at inner shelf stations where it was collected most often during winter (Figure 5.25). It occurred in 67% and 20% of the suction and grab samples collected in winter and summer, respectively. The number of specimens in our samples indicates that Podocerus sp. was significantly more abundant in winter than in summer (P < 0.05, Mann-Whitney U-test). The caprellid amphipod Luconacia incerta was also collected at all stations but was most abundant in inner and middle shelf live bottom areas (Figure 5.26). It was most frequently encountered in winter, when it occurred in 70% of the suction and grab samples, but it was present in only 31% of the summer collections. No significant difference in abundance of L. incerta was noted between winter and summer (P > 0.05, Mann-Whitney U-test) * The distribution of Erichthonius sp. A was limited to the outer shelf (Figure 5.27). The abundance of Erichthonius sp. A did not differ significantly between sampling periods (P > 0.05, Mann-Whitney U-test). This species was collected in 12% of the suction and grab collections taken in winter and in 24% of those taken in summer. The ophiuroid, Ophiothrix angulata, was most abundant at stations IS02 and IS03 (Figure 5.28). It was inCrequently collected and not very abundant at outer shelf live bottom sites. In winter, 0. angulata occurred in 53% of the suction and grab samples and was found in @_82% of those taken in summer. No significant difference in abundance was noted between winter and summer (P > 0.05, Mann-Whitney U-test). Community Structure - Community structure measures of Shannon diversity 116 (H'), evenness (P), richness (SR), number of species (.@.) and number of individuals W were used primarily to compare faunal assemblages between stations. For completeness and for reference we have also included a listing of these measures for each collection arranged by station and sampling period (Appendices 12 and 13). The values of H' were generally similar between stations for both sampling Peri ds. Noted exceptions occurred at stations IS02 and IS03 in suvAner,and I ton MS01 in both winter and summer (Figure 5.29; Table 5.14), where low H' values were associated with a relatively high abundance of invertebrates and low evenness. Low evenness values were attributed to the overwhelming dominance of inner and middle shelf stations by the colonial polychaete Filograna implexa and of samples from outer shelf station OS03 by f. implexa and Phyllochaetopterus socialis. Furthermore, the substantially lower values of V at these stations were also a function of the highly contagious distribution of these polychaetes. Most of the other stations had evenness values above 0.60, indicating a fairly even distribution of individuals among species. The lack of a strong trend between H' and depth was also noted for individual collections (Figure 5.30). It is of interest that H' values for collections from inner and middle shelf depths were less variable (as indicated by the tight clumping of points) than those associated with collections from the outer shelf. The difference in variability between diversity values for these collections probably is related to sampling efficiency of the suction sampler versus that of the grab (see Chapter 8). Richness corresponded closely to the number of species (Table 5.14). The number of species was found to be significantly different between stations for winter (P < 0.05) and slimmer (P < 0.05) by the Kruskal-Wallis test. Lowest values occurred at station OS02 in winter and station IS01 in summer. Otherwiset the richness values were similar between stations and agreed remarkably between sampling periods for a single station. The number of individuals collected was lowest at stations OS02 and IS01, both of which also had low values of s and SR. Differences in abundance were statistically significant between sta@-tions during winter (P < 0.05) and summer (P < 0.05). No apparent trend in abundance was noted between stations sampled in summer, but fewest individuals were collected at outer shelf stations during winter. Although H' and its components are important indices for interpreting community structure, they do not fully explain the composition of the community in terms of relative proportions of dominant and rare species. Therefore, we constructed dominance diversity curves for each station based on the numerical relation of individuals to species (Figures 5.31 - 5.39). Results were similar for all stations during both sampling periods in that the majority of species was represented by one or a few individuals. An extension of the dominance diversity curve to the right clearly reflects the presence of many rare species. Species which were represented by one or two individuals accounted for 49% - 1 71% of all species collected during winter, while the range of percentages in slimmer was 52% - 79%. In contrast to the large number of rare species, numerically dominant species were few, as expressed by low values (< 40%) of the dominance index (DI). The high values observed at station MS01 and IS02 were in part due to overwhelming dominance by Filograna implexa and Phyllochaetopterus socialis at these stations. I I Species Assemblages and Distributional Patterns - Normal cluster analysis of 42 collections taken with suction and grab samplers during winter produced 117 3@40 800 South Carolina -INVERTEBRATE DIVERSITY 34* Cr H' `,CHARLESTON- 9IS01 320_@ S VANN H 90sol 820 MS02 Georgia 320 *OS02 IS02 @B R U N OMS03 *OS03 OIS03 JACKSONVILLE:_ so* Figure 5.29. Shannon diversity (H') for pooled replicate samples of In invertebrates at each station durino winter and sum er, 1980. 118 Table 5.14. Community structure values [number of individuals, number of species, Shannon diversity (HI), evenness (J'), and richness (SR)I for pooled replicate samples of invertebrates at each station during winter and summer, 1980. No. No. Sta ion Season Individuals Species H' if SR winter 1737 243 5.98 0.76 32.44 summer 222 92 5.74 0.88 16.84 IS02 winter 2250 229 6.05 0.77 29.07 summer 4526 193 1.43 0.19 22-81 IS03 winter 2874 263 6.11 0.76 32-90 summer 1368 240 6.63 0.84 33-10 MS01 winter 6528 236 2.56 0.32 26.75 summer 3180 212 2.99 0.39 26.16 MS02 winter 1202 166 5.62 0.76 23.27 summer 592 144 5.81 0.81 22.40 MS03 winter 1099 205 6.33 0.82 29-13 slimmer 992 193 5.38 0.71 27.83 Osol winter 425 144 6.21 0.87 23-63 summer 968 148 4 .62 0.64 21.38 OS02 winter 129 48 4.73 0.84 9.67 summer 1060 157 5.64 0.77 22.39 OS03 winter 616 159 6.39 0.87 24.60 stumer 8257 242 3.10 0.39 26.72 119 6- 0 0 0 00 C: 0 5- 0 0 0 0 0 0 0 0 Cn @ 0 0 d:)0 Cr 8 0 00 0 0 W 0 0 0 Cn 8 W 0 CL 0 0 0 0 10 20 30 40 50 60 70 DEPTH(m) Figure 5.30. Scatterplot showing Shannon diversity (H') in relation to sampling depth. Closed circles represent winter collections, and open circles represent summer collections. 120 500- STATION ISOI 0100-.. *WINTER D.ZaZ3.9% SUMMER 0.1- 19.4 % U. 0 w .10- C12 amt to 243 16 1 310 1 510 70 90 110 130 SPECIES SEQUENCE Figure 5.31. Dominance diversity curve and dominance index MI.) values for invertebrates collected by the suction sampler at station IS01 during 1980. 121 3938 o 500- STATION ISOZ 100 -WINTER D.I.-IT.3% SUMMER D.I.- 88% > z 0 % 0 0 0 cc do w 10- GD OD C12 - 0 z @Ccffl. to 193 Cwt. to Z29 1b 3'0 50 @0 @0 110 1@0 150 170 SPECIES SEQUENCE Figure 5.32. Dominance diversity curve and dominance index (D.I.) values for invertebrates collected by the suction sampler at station IS02 during 1980. 122 500- STATION IS03 100- -i D CID WINTER D.I.wIT.5% SUMMER D.I.-12.3% z LL. 0. 0 90 11@ w 'Mco w lo- co 00. z co.U to 251 to 240 io io io io I io lio lio SPECIES SEOLIENCE Figure 5.33. Dominance diversity curve and dominance index (D.I.) values for invertebrates collected by the suction sampler at station IS03 during 1980. 123 10000- 1000- 9) STATION IVISOI > -0 @WINTER D.I.=75.5% o SUMMER D.I.=73.1% 100- ILL. 0 0 w 0 0 0 0 0 z 06 10- =6 awcont. to 212--mont. to 236 10 30 50 70 90 110 130 150 SPECIES SEQUENCE Figure 5.34. Dominance diversity curve and dominance index (D.I.) values for invertebrates collected by the suction sampler at station MS01 during 1980. 124 1000- co -j 100- STATION MS02 WINTER D.I.z27.8% 93 0 o SUMMER D.I.=24.7% 0 LL. 0 - I 0 w 0 to 0 Io- w - CID OMM) (MINOR) GREW) COVER cont. to 144 COMORO"" "-...-....cont. to 166 1 1 1 1 1 10 30 50 70 90 120 SPECIES SEQUENCE Figure 5.35. Dominance diversity curve and dominance index (D.I.) @alues for invertebrates collected by the suction sampler at station MS02 during 1980. 125 327 -0 50- STATION MS03 00 WINTER D.M.-13.9% o SUMMER D.I.z39.0% 0 10- U- 0 a@ I% Uj 03 GM10cont. to 193 to 205 1 1 1 30 50 70 90 110 SPECIES SEQUENCE Figure 5.36. Dominance diversity curve and dominance index (D.I.) values for invertebrates @ollected by the suction sampler at station MS03 during 1980. 126 1000- STATION OSOI 100- n WINTER D.I.=16.5% o SUMMER D.l.z44.9% z 0 0 0 0 0 w w I CID 0 Io- 0 z Mao CtD -*-Now cont. to 144 ammumcont. to 148 10 30 50 70 SPECIES SEQUENCE Figure 5.37. Dominance diversity curve and dominance index (D.I.) values for invertebrates collected by the grab sampler at station OS01 during 1980. 127 1000- 0 U) 100-0 -i 0 0 STATION OS02 > - a - - - WINTER D-1. a 29.5% z o SUMMER D.1.z 25.6% 00 U. 0 0 0 0 0: ao w 0 w Co 10- OM z ee 000MMD cont. to 157 10 30 5'0 70 90 SPECIES SEQUENCE Figure 5.38. Dominance diversity curve and dominance index (D.I.) values for invertebrates collected by the grab sampler at station OS02 during 1980. 128 5000- 0 1000 500- co -i M 00 0 1 STATION OS03 > 100- z *WINTER D.I.-13.8% aSUMMER D.I.-71.1% LL 0 0 w 00 z 10- 41 ft 159 amcw". 242 16 510 1 @0 @0 11,0 , 1;0 15,0 SPECIES SEQUENCE Figure 5.39. Dominance diversity curve and dominance index (D.I.) values for invertebrates cQllected by the grab sampler at station OS03 durinq 1980. 129 5 groups (Figure 5.40). Stations were generally grouped in accordance with their depth zonation on the continental shelf; however, collections from inner and middle shelf live bottom areas formed two groups of collections from each depth zone. Thus, collections from station IS01 were distinct from those taken at stations IS02 and IS03, and the quantitative composition of middle shelf collections in group 3 was different from that of collections in group 4. Outer shelf collections, on the other hand, formed one major agglomeration which was not very similar to other station groups. It is difficult to deter- mine whether outer shelf stations differed from other sites solely because of faunal composition or because of disparate sampling methods between inner, middle, and outer shelf sites. Without using the same gear at all sites, it cannot 'be conclusively stated whether outer shelf stations have different organisms. Results of cluster analysis of summer data were not as clear. Classifi- cation of the 45 collections formed seven groups which were not all readily explainable in terms of location (Figure 5.41). For example, groups 2, 3, 4, and 7 each consisted of collections from either the inner, middle, or outer shelf live bottom habitats, whereas groups 1, 5, and 6 were composed of collections from more than one area of the shelf. When compared with the relatively high integrity of collections within a site group for the winter data, these results suggest that the quantitative composition of the live bottom community was much more homogeneous across the entire shelf during slimmer. It further implies that strong zonation of the fauna did not occur at that time. Ordination of suction and grab collections helped to clarify zonation patterns and pointed out several misclassifications which occurred during cluster analysis. Axes 1 and 2 of the station ordination for winter data together accounted for 26.06% of the total eigenvalue and jointly distinguished outer shelf collections (i.e., members of cluster group 5) from inner and middle shelf collections (Figure 5.42). However, three samples from site group 5 were closer to members of group 4 in the two-dimensional ordination space, suggesting that these seemingly aberrant collections may have been misclassified by the normal cluster analysis. In general, constituents of middle shelf site group 4 had intermediate scores on axis 1, while members of inner and middle shelf site groups 1, 2, and 3 had high scores on axis 1. Axis 2 successfully separated members of inner shelf site group 1 from consti- tuents of groups 2 and 3; however, the overlap among members of the latter two site groups on both axes 1 and 2 suggests that any differences in faunal compo- sition between the two groups may have been exaggerated by cluster analysis. Ordination of summer data revealed that neither axis 1 nor axis 2 alone was successful in separating all collections taken in any one shelf area from collections taken in other areas. These two axes accounted for 30.89% of the total eigenvalue. The ordination results confirm those of the normal cluster analysis; namely, that strong zonation of the fauna with respect to bathymetry is apparently not as pronounced in the summer as it is in the winter. Certain collection groups defined by cluster analysis retain their integrity in the two-dimensional ordination space, however. Notably, outer shelf site groups 6 and 7 are largely self contained entities in the lower left hand corner of - the ordination space (although one collection from site group 7 is distinguished as an 11outlier"-by its unusually high abundance of the colonial polychaete Phyllochaetopterus socialis) (Figure 5.43). Similarly, constituents of inner and middle shelf site group 1 formed a cohesive group in the upper middle portion of the ordination space. Members of all other collection groups (particularly site groups 3 and 5) were widely distributed and showed no apparent 130 Suction and Grob: Station Groups SIMILARITY .8 .6 .4 .2 0 -.2 -.4 -.6 Group Station IS03 IS03 IS03 IS03 IS03 IS02 IS02 IS02 IS02 IS02 ISM isol ISM isol ISM QSU2_ MS02 MS01 3 MS01 MS01 MS01 MS03 MS03 MS03 MS03 4 MS02 MS02 MS03 OS02 OSO1 OS02 OS03 0$02 5 0$03 OS03 OS03 0$01 OSO1 OSO1 OSO1 OS03 .8 .6 .4 .2 0 .2 -.4 -.6 SIMILARITY Figure 5.40. Normal cluster dendrogram of winter suction and grab-collections indicating station groups formed by a combination oficanberra metric similarity coefficient, square root transformation, and flexible sorting. 131 Suction and Grob: Station Groups SIMILARITY -.3 Group Station IS03 MS03 IS02 IS02 IS02 IS03 ISO3 IS03 IS03 SOZ MMSO I MSOI 3 MS01 MSOI MSOI MS03 Fs- 0 - - - 4 ISO: IS01 - 003- - - MS03 IS01 IS01 OS03 5 1502 MS03 OS02 IS02 MS02 OS03 - MS02 ws- 0 2- MS02 OSO1 - OSO1 OSO I OSO1 0301 OS03 OS03 OS02 OS02 OS02 0 OS02 -!1 -13 SIMILARITY Figure 5.41. Normal cluster dendrogram of summer suction and grab collections indicating station groups formed using the Canberra metric similarity coefficient, square root transformation, and flexible sorting. 100- OOS02 OOSOI OOSOI Cluster 90- Groups 1 0 so- 2 3 OOSOI OOS03 4 70- OOS03 OOS03 IS020 5 0 OOS02 IS020 OOSOI OOS03 IS020 N 60- IS030IS030 IS030 OIS03 50- OOSOI OIS03 X OIS020IS02 41 40- OS030 AMS03 30- A MS02 OISOI 6MSOI IS01 20- MS02A& A IS0191;-le, NISOI MS03 MS03 MSOI 6 MS02 10- MS03A 6 MS02 6MSOI 6MSOI OOS02 6 MS03 0 OS02E]SIS01 0 10 20 30 40 50 60 @O @O @O 100 AXIS-I Figure 5.42. Results of reciprocal averaging ordination showing orientation of winter suction and grab collections at stations on axes I and 2. Symbols indicate which group these collections were placed into by cluster analysis. M ON M so so an (OR OW Ilft- no a* 10" 40 so 10 so M WO Wit, We MW- MP WO 4401 00 MW NO: NO 1111011@ 10 MV go 100 OIS02 IS020 OIS02 Cluster 90- 0 MS03 Groups Alsol 1 0 80- Alsol 2 0 OIS03 0 OIS03 3 a IS020 I= IS039 0 6MSOI 6MS01 4 A 70- 6MSO1 5 0 ISOIA IS03 ISOIOOMSO? 0 MS03 6 a 6 MS02 0 IS036 M S02 7 0 N 60- OMS02 6MS01 0 MS03 250- M MS02 C] OS02 45 M S03 X OOS03 40- OS02 0 MS03 0 OS02 OOS02 OOS03 6MS01 8 OOS03 30- OSO1 OS02 16osm(OsOl 20-0 0osol IS020 OSO1 10 00 S03 OS03 ;j 0 1 1 1 1 1 1 0 10 20 30 40 50 60 70 so @O 100 AXIS I Finure 5.43. Results of reciprocal averaging ordination showing orientation of summer suction and grab collections at stations on axes 1 and 2. Symbols indicate which group these collections were placed into by cluster analysis. 134 trends with respect to either ordination axis. The most deviant members of collection groups 3 and 5 had the highest scores on axis 1, however, and all were distinguished by large numbers of another colonial polychaete, Filograna implexa. The classification of 105 species remaining after reduction of winter dat4 produced seven groups (Table 5.15). Nodal constancy and fidelity diagrams (Fi#lre 5.44) revealed that the groupings were interpretable in terms of stition location. Species in group A were very highly constant at inner shelf stations IS02 and IS03, and were infrequently collected at MS01. Those species in this group which were entirely restricted to inner shelf stations during winter included the amphipod Amphithoe sp. A and the annelids Eulalia macroceros and Pista quadrilobata. As indicated by the cluster hierarchy shown in Figure 5.44, species in group B were most similar to those in group A with respect to distribution. Group B species were highly constant in collections from IS02, IS03, and MS01, although they were generally more ubiquitous than group A species, and none were restricted to collections from inner shelf live bottom areas. Group C species were frequently collected at inner and middle shelf stations. In accordance with their ubiquitous distribution, this group was not faithful to any one station. The numerically dominant amphipods Luconacia incerta and Podocerus sp., polychaetes Spiophanes bombvx and Exogone dispar, and the echinoderm.0phiothrix angulata occurred in this group. Species in group D were widespread but generally uncommon across the shelf. The only numerical dominant belonging to this group was the syllid polychaete Syllis spongicola. Group E species were very constant and faithful at station MS01. This group was also encountered at other stations from inner and middle shelf.live bottoms but was not very common. Species in groups F and G were characteristic of the inner shelf live bottom habitat and consistently occurred in collections from stations IS03 and IS01, respectively. These species were not faithful or constant at any other sites where they occurred. Groups formed by classification of 123 species from summer collections differed from those generated for winter data because of the presence of definite outer shelf assemblages (Table 5.15, Figure 5.45). Otherwise, results from the two seasons were similar with predominantly ubiquitous inner and middle shelf live bottom assemblages represented in collections from both winter and summer. Species in groups A and B were most consistently collected from outer shelf live bottom areas, especially OSO2. Group A species were largely restric- ted to stations OS02 and OS03 and all members of the group were collected at these stations at least once. Group B species were not restricted in such a manner and displayed only low to moderate constancy for all sites except OS02 where it was consistently collected. Only the amphipods Unciola sp. A and Erichthonius sp. A, and the polychaete Syllis sp. D were limited to outer shelf stations. As indicated by the cluster hierarchy of Figure 5.45, little similarity existed between groups A and B and others formed by cluster analysis. Ubiquitous shelf species formed groups C and E. Those in group C were generally uncommon and displayed only low to moderate constancy at ill sites. The numerically dominant species Spiophanes bombyx and Podocerus sp. were included in group C. Group E contained spec@ies w@hich were not consistently encountered anywhere except station IS03. 135 Table 5.1.5. Species groups resulting from numerical classification of data from samples collected by suction and grab samplers during winter and summer, 1980. (Am - Amphipoda; Br = Branchiopoda; Cu Cumacea; D - Decapoda; E - Echinodermata; I = Isopoda; M - Mollusca; My =-Mysidacea; P Polychaete; Po Porifera; Py = Pycnogonida; Si - Sipunculida; T = Tanaidacea). Winter 1980 Slimmer 1980 Group A Group A Ampithoe sp. A (Am) Ampelisca sp. B (Am) Eulalia macroceros (P) Gl):cera capitata (P) Pista quadrilobata (P) Syllis cornuta (P) Musculus sp. A (m) Chaetozone setosa (P) Pherusa ehlersi (P) Terebellidae C (P) Sabellaria vulgaris beaufortensis (P) Polydora caeca (P) Group B Group B Anachis iontha (M) Onuphis pallidula (p) Ap ra -M2,gnifica M Spio pettiboneae (p)' Microdeutopus myersi (Am) Photis sp. (Am) Titrella lunata (M) Ampelisca vadorum (Am) Tellina sp. (M) Ameharete acutifrons (P) Megalobrachium soriatum (D) Phyllodoce longipes (P) Elasmopus sp. A (Am) Prionospio sp. B (P) Pseudomedaeus A&as!@izii (D) Unciola sp. A (Am) Lembos unicornis (Am) ErichtKonius sp. A (Am) Websterinereis tridentata M 3@-uphis nebulosa M Pherusa inflata (P) Accalanthura crenulata (1) Lumbrineris inflata (P) Sthenelais boa M Syllis gtraciTI-s7P)' Genocidaris maculata (E) Branchiosyllis oculata (P) Syllis sp. D M Syllis regulata carolinae (P) Glycera sp. B M Podarke obscura (FT - Armandia maculata (P) Synalpheus townsendi (D) Psammolyce ctenidophora M Odontosyllis fulgurans M Group C Group C Leptochelia sp. M Gammaropsis sp. (Am) Glycera tesselata (P) Cavrella equilibra (Am) Phtisica marina (Am) Melita appendiculata (Am) Mexalomma bioculatum (P) Luconacia incerta (Am) Chone americans (P) Photis sp. (Am) Autolytus sp. (P) Erichthonius brasiliensis (Am) Eunice vittata (P) Podoceros sp. (Am) Chrysopetalidae A (P) Pagurus carolinensis (D) Eulalia sanguinea (P) Paracerceis caudata (1) Polycirrus carolinensis (P) Ampelisca agassizii (AM) Ceratonereis mirabilis (P) Ophiothrix angulata (E) Le2tochela papulata (D) Aspidosiphon ApiiLalis (SO Hydroides sp. A (P) Lembos smithi (Am) Pomatoceros americanus M Loimia medusa (P) Spiophanes bombvx (P) Prionospio cristata (P) Owenia fusiformis (P) Owenia fusiformis (P) Pagurus hendersoni (D) Mediomastus californiensis (P) Harmothoe sp. A (P) Ampelisca vadorum (Am) Melita appendiculata (Am) Axiothella mucosa M Podocerus sp. (Am) Ampharete americans (P) Unciola laminosa (Am) Sicyonia laevigata (D) Yr-ichthonius brasiliensis (Am) Exogone dispar M Alpheus normanni (D) Sabellaria vulgaris vulgaris (P) Eunice vittata M Group D Oxyurostylis smithi (Cu) Chrysopetalidae A (P) Lysianopsis alba (Am) Amphiodia pulchella (E) Aspidosiphon misakiensis (Si) Polycirrus carolinensis (P) Apanthura magnifica (1) Eulalia sanguinea M Tellina sp. (M) 136 Table 5.15 (Continued) Winter 1980 Summer 1980 Syllis hyalina (P) Cinachyra kuekenthali (Po) Laonice cirrata (P) Craniellidae B (Po) Phtisica marina (Am) Natica Pusilla (M) ,@p-h-ane@-s ,to,b iLi Ix (P) Corbula dietyiana (M) Glycera tesselata (P) Fista palmata (P) Group E Group D Laonice cirrata (P) Spionidae B (P) Phyllodoce fragilis (P) Crassinella lun@lata (M) Chrysopetalidae B (P) Prionospio cristata (P) Autolytus sp. (P) Gouldia cerina (M) Phyllodoce longipes (P) Goniadides carolinae (P) Anoplodactylus petiolatus (py) Axiothella mucosa (P) Lumbrineris impatiens (P) Paraprionospio pinnata (P) Group F Spio pettiboneae (P) Syllis sp. D (P) B niella portoricensis (My) Syllis spongicola (P) Varicorbula operc lata (M) Chone americana (P) Tellina americana (M) Crassinella lunulata (M) Laevicardium pictum (M) Anchialina typica (Mv) Group E Thelepus setosus (P) Phyllochaetopterus socialis (P) Cinachyra alloclada (Po) Erycina linella (M) Caprella I @ntis@(Am) Tellina sybaritica (M) Megaluropus sp. (Am) Glottidia pyramidata (Br) Ophiostigma isacanthum (E) Mesochaetopterus sp. (P) Bodotriidae B (Cu) Scolelepis texana (P) Thor sp. (D) Batrachonotus fralzosus (D) Syllis alternata (P) Paraprionospio pinnata (P) Amphipoda E Amphiodia pulchella (E) Maera sp. A (Am) Malacoceros glutaeus (P) Group G Leucothoe spinicarpa (Am) Cinachyra alloclada (Po) Group F Lima pelucida (M) Eunice filamentosa (P) Homaxinella waltonsmithi (po) Loimia medusa (P) Carpias bermudensis (I) Nassarius albus (M) Polycirrus eximius (P) Pilumnus floridanus (D) Protodorvillea kTfersteini (P) Pherusa inflata (P) Cinachyra keukenthali (Po) Cumingia coarctata (M) Pelia mutica (D) Exogone dispar (P) Megalomma bioculatum (P) Nicomache trispinata (P) Tanaidacea . A Anoplodactylus petiolatus (Py) Strombiformis bilineatus (?) K Syllis alternata (F) Arabella mutans (P) Luconacia incerta (Am) Hydroides sp. A (P) Group H Group G Scypha barbadensis (Po) Pteria colymbus (M) Clathrina coriacea (Po) Harmothoe sp. A (P) Chione grus (M) Inachoides forceps (D) Syllis hyalina (P) Unciola laminosa (Am) Leucothoe spinicar2a (Am) Gouldia cerina (M) Phyllocarida Lysianopsis alba (Am) Thor sp. (D) Pseudeurythoe ambigua (p) Tanaidacea B Latreutes parvulus (D) Mediomastus californiensis, (P) Gitanopsis sp. (Am) Lysidice ninetta (P) Leptoche papulata (D) Pseudeurythoe ambigua (P) Bowmaniella portoricensis (My) Anachis hotessieriana (M) Aspidosiphon misakiensis (Si@ Nassarina minor (M) 137 Table 5.15 (Continued) S-,@er 1980 Filograna implexa M Group I Phyllodoce fragilis (P) Syllis gracilis (P) Podarke obscura (P) Pagurus carolinensis (D) Websterinereis sp. A (P) Lembos unicornis (Am) Malacoceros glutaeus (P) Meg lobrachium soriatum (D) Pista quadrilobata (P) Sipunculida A Synalpheus townsendi (D) Lembos smithi (Am) Elasmopus sp. A (Am) Paracerceis caudata M Pelia mutica (D) Aspidosiphon spinalis (Si) Lumbrineris inflata M Ampelisca agassizi (Am) Ophiothrix angulata (E) Syllis spongicola (P) 138 -0-6- SPECIES GROUPS -0.4- -0-2- 0] A B C D E F G ........... ..... .......... IS03 IS02 ........... .... .... CONSTANCY U) IS01 N20.7 Very High Z0.6 High 0 MS03 ..... ... MS02 [email protected] Moderate ........... MS01 OS03 E]20.1 Low OS02- < 0. 1 Very Low 0S01 A B C D E F G IS03 ....... .... IS02 FIDELITY ..... ... ..... . . . . . . . . . . ........... Cn TS01 M24 Very High z 0 MS03 Z3 High ................ ... ................ . .............................. ......... . .. . ..... ....... . . .......... ........ MS02 ........... > 2 Moderate MS01 . .... I Low OS05 r-l< I Very Low 0soz 0S01 .............. Figure 5.44. Inverse classification hierarchies and nodal diagram showing constancy and fidelity of station species group coikidence based on winter suction and grab collections. 139 SPECIES GROUPS -04- -0.2- o- F-1 A 8 C 0 E F G H I IS01 IS02 IS03 . . . . . . . . . . . . . . . CONSTANCY C0 z MS01 W107Very High 0 ...... [email protected] High MS02 . .. .......... E5 >0.3 Moderate MS03 E@20-1 Low 0S01:,: 0so < 0. 1 Very Low OS03 A B C D E F G H I isol IS02 FIDELITY IS03 Cn . ....... z MS01 >4Very High 0 EM23 High MS02 Q22 Moderate MS03 0S01 E@21 Low <I Very Low OS02 OS03 Figure 5.45. Inverse classification hierarchies and nodal diagram showing constancy and fidelity of station species group coincidence based on summer suction and grab collections. 140 Relatively uncommon and unfaithful species were found in groups D and F. The only numerically important constituent of these groups was PhyllochaetS@R7 terus socialis (group F). The remaining species groups were somewhat ubiquitous but were most common at inner and middle shelf stations. Specifically, species in assemblage G w e highly constant at stations IS03 and MS01. They were also highly faith- ful o MS01. The abundant species Exogone dispar and Luconacia incerta were m rs of this species group. Those species forming group H were most cons-istently encountered at station MS03; however, their faithfulness to this station was only moderate. The colonial polychaete Filograna implexa was an important constituent of this group. Species in group I were common at station IS02 but displayed only low to moderate constancy elsewhere. The numerically important species Syllis spongicola.and Ophiothrix angulata were members of this group. A comparison of the associations among selected species from the winter and simmer sampling periods is presented in Figure 5.46. Although most species co-occurred only during one season, there were a surprising number of co- occurrences during both seasons. Among these was the association of the annelids.Eunice vittata, Chrysopetalidae A, Eulalia sanguinea, Spiophanes bombyx, Polycirrus carolinensis, and Owenia fusiformis; and the amphipods Melita appendiculata and Phtisica marina. These species were ubiquitous during both seasons, although in winter they were most frequently encountered at inner and middle shelf live bottom areas. Another conspicuously recurrent assemblage was composed of the hermit crab Pagurus carolinensis, the amphipods Ampelisca agassizi and Lembos smithi, the isopod Paracerceis caudata, the echinoderm Ophiothrix angulata, and the sipunculid Aspidosiphon spinalis. These species were most constant at inner and middle shelf stations, although they were also collected at sites across the shelf. DISCUSSION Diversity of the Live Bottom Communities: The results of the benthic analysis clearly emphasize the diverse and complex nature of South Atlantic Bight live bottom communities. The number of invertebrate taxa. identified in collections from all sampling devices at our study areas totaled 1175. The faunal richness observed in these habitats can be better appreciated when compared with results of other studies; although, few comparable studies of this magnitude have been conducted along the Atlantic coast of the United States. While fully realizing that inequities exist in sampling methodology and extent, as well as in the level of taxonomic identi- fication, we can loosely compare our results with those from other hard bottom studies in the South Atlantic Bight, from sand biotopes in the same area, and from the outer continental shelf region of the Middle Atlantic Bight. One of the first explorations of hard bottom areas in the South Atlantic Bight was conducted by Pearse and Williams (1951) who collected 240 inverte- brate species and 102 species of algae from inshore "Black Rocks" off North Carolina. The taxonomic groups of major importance on these rocks Included decapods, mollusks, polychaetes, sponges, and bryozoans. Later Meniies et al. (1966) collected 107 identifiable species by dredge on a lithothamnion "reef" w e of the outer shelf off North Carolina. Cain (1972) subsequently added 37 more species to this list which was dominated by decapods, hydroids, and gastropods. (D @n r 'b (A 0W 0 n -h P Zt X :3. Cb c: o-, r- r- C -h (D 0 0 n) N..% I%z - 'o C+ a a a n 0 C1+ m t< 0 (D c+ m 0 C-+ C% CA c b (A 0) 0 o"T =r -h Cr :3 Q >'o 4' a 0 @ @ i @@ 73 @-. . I . - 2 ij -0 0 (A - :E Phtisica marine (D -1 ct :3 -. * -AiI I 1* 10 0 0 14010101010 0 40 0 to C+ < :3 00 0 so 4p 0 0 0 0-w-onto fusformis 01016191010 0 0 * * 0 0 -5 C+1 0) m (m 0) :3 :E 7r -3 C7 0 r, m (A 0 0 0 0 6191010 0 0 0 0 019 9 0 e Polycirrus caroliflonso :3, :3 m 0 OOOo*OOOOOO splophones boinbyx Wr_ C+ 1 010101 Jii (A fD CL 0 0 0 0 00000000049- EU10110 songuifloo -,h -'I r- @ 0 0 0 * *1* 4910 0 *-0 Chrytopetalidoe A 10 -5. c 0 - - - *IOM Eunice vitiate 0 - in c \L-LJ- A - - - 0 0 o Ol* Ole 0 010101*1010 0 :3 C+ -1 Lembo$ unicornis CL(C CD -3 MAI- I no -1 fD I Ibk Lumirinerls ififlato C+ w =3 Syllis sponvicold C+ a 0 1 w - = CD I id Wormothoo sp. A M(D E C+ 0) Autolrfus sp. a) (D CD - 0 pogurus hentforsoni (Aa -I -S 1< --h C+ Do LA arenchlosyllis ocil/0a C+ Ln W -. tA relfina sp. 4@- 10) 0) tA -0 1 1 1 . I I I I a E3 CD P.60fuso inflato -0 -0 0 0 Amphio pulchollo ct @ - -.% -. *1* 0 0 Ole e *I* * *101010 *1 0) (D 0 0 0 0 Ole 0 * 0 0 0101010 01 sabollaria vulgaris C+ 04000 00 '610 9 0 0 0 0 sicyopid /08vigoto 0 +%010 0 :E m ER 91 0 Ole 0 0 0 0 0 01*10 0 Axiotholla mucoso =1 =r 0 C+ -. 1-i 0.0 0 0 0 0 9 01010 9 @G-pwisco vadorum LA C+ * w * - Z x z Ole * 0 q 0.* 0 *1*[* 0 Pholis s P. L11 0 C: C: (A -0 ic -4 x -4 0 0 OL* 0 0 61610 Luconocia incerto 00 (D r. m rn m m;D Caprollidoe A m 0 0 0 *[* 4D 0 Ole * C (D C 0- =r To 0 0 * Ole 0 0 * * 9 oityurostylis smithi -S (A (D 7\ *14 e 0 Ol 0 0, syllis hyalina CL -1 Eta *1* *10 010 01 Loimio moduse m :E m -1 Exogone dispor C:1. CD -1 0) 0) 0 *1 -1 cr =4 Lembos smithi 14A ID 0 0 0) (D EA CD 0 -For-acorc*is coudato C+ 0) ";is-pdospho 23 (M 0 n Spina IV -0 -1 0 0 ophiothrix onvulato Ln 0 & Ampolisco ogoss4ri C) "a Pagurus cgrolinonsis @-k U:) Podlocerus sp. Erichthoniu 4brosifi* 142 In a study which demonstrates the complexity of microhabitats found on hard bottoms, McCloskey (1970) collected 56,616 individuals belonging to 309 invertebrate species from eight heads of a scleractinian coral, Oculina arbuscula. Continental Shelf Associates (1979) collected 499 total identifi- able taxa in 68 dredge hauls on hard bottom within four lease blocks off Geo ia. Frequently occurring taxa associated with hard substrata included theJecapod crustaceans, anthozoans, bivalves, bryozoans, and echinoderms. In -ew of these reports, the present study provides much new information on the importance of the bryozoans, cnidarians, and sponges among the megafauna, and the polychaetes, mollusks, decapod crustaceans, and amphipods among the macrofauna. Studies by Frankenberg (1971), Day et al. (1971), Frankenberg and Leiper (1977), George and Staiger (1977), and Tenore (1978) on invertebrate fauna from sandy substrates in the South Atlantic Bight illustrate the differences in biomass, faunal composition, and richness between sand and hard bottom habitats. Frankenberg (1971) collected monthly grab samples from a coarse sand bottom area off Georgia in 21-m depth and found a total of 235 species 12 m72 over a 12-month period. In comparison, suction samples taken-at our Gray's Reef station (IS02) off Georgia in equivalent depths collected 329 species m_2 with only two seasons represented. Day et al. (1971) found diversity was highest at a station off North Carolina which was characterized by lumps of sponges and ascidians. Similarly, George and Staiger (1977) attested to the high invertebrate biomass of one hard bottom area sampled by trawl off Charleston. They found that dominant sand bottom megafauna were holothurians, asteroids, cephalopods, and decapod crustaceans, whereas the high biomass observed at their hard bottom site was due to sponges, tunicates, and soft coral. Tenore (1978) attributed high values for total number and diversity of benthic macroinfauna in the South Atlantic Bight to the occurrence of scattered hard bottom reef communities. When compared to results obtained by Boesch et al. (1977) for macrofauna in the Middle Atlantic Bight, the South Atlantic Bight fauna appears to be more diverse. Generally, fewer than 60 species were taken in six replicate 0.1 M2 grab samples from inner or central shelf stations of the Middle Atlantic Bight, and the greatest diversity (up to 141 species) occurred in outer shelf swales (Boesch et al. 1977). A large number of uncommon or rare species contributed to the high diversity observed during this study. Although others (Day et al. 1971, Davis and Spies 1980) have pointed out that rare species are subject to sampling error and should not be used to describe faunistic patterns, we feelthey are an important component of the live bottom biocoenotic complex. In fact, examination of stomach contents of several fish species (see Chapter 7) demonstrated that with few exceptions, species of invertebrates which were not commonly collected by our sampling efforts formed a considerable part of the fishes' diet. Dominance diversity curves, which approximated the lognormal distribution, emphasized the importance of rare species in live bottom communities. Our curves differed from those by Whittaker (1970) for the lognormal distribution of land plants because we collected fewer species with medium abundance and more rare species. The lognormal distribution is appropriate when the number of species is large and the factors determining their relative importance are complex: and multiplicative in effect (Whittaker 1965). 1 The high diversity of live bottom habitats noted in our study is due, in part, to the complexity of bottom types as compared With surrounding sand bottom areas. Substrate composition in all study areas consisted of a mosaic 143 of different microhabitats including rock crevices, bare rock, rock tops with a layer of sand, and sand patches between rocks. The complexity of these habitats allows many similar species to coexist. Microbabitat complexity is further enhanced by the presence of certain organisms which support a variety of other species. This has been demonstrated for the coral Oculina varicosa by McCloskey (1970), and the sabellarid worm Phragmatopoma lapidosa by Gore et al. (1978). In our study, the larger sponges such as Ircinia campana and Spheciospongia vesparium and colonies of the worms Filograna implexa and Phyllo haetopterus socialis appeared to perform a similar function. Sponges are apparently less important at live bottom stations sampled off North Carolina. There, algal species are an important constituent of the community in terms of diversity, abundance, and role as a microhabitat (Vol. II, Chapter 5). In addition, the complexity of live bottom areas, with their component microhabitats, can increase protection afforded to prey species. As Smith (1972) has pointed out, refuges where prey populations can maintain themselves are important in the maintenance of community structure. No doubt, some predators find only limited access to small invertebrates which are sheltered among soft corals, sponges, and polychaete tube mats. Species diversity is also enhanced through competition among constituent epifaunal species. This can lead to various specializations which allow many species to coexist in a limited space (Menge and Sutherland 1976). Differential growth patterns can also contribute to higher diversity (Jackson 1977). For example, Osman (1977) has noted that bryozoans normally do not overgrow another colony of the same species but, rather, reorient their growth to avoid this. By extending growth upward, many sponges, hydroids, octocorals, and tube building polychaetes are also able to avoid overgrowth by encrusting forms. Additionally, invertebrates such as large sponges reduce intraspecific competition by virtue of their widely spaced distribution. Finally, presence of a variety of sessile invertebrates creates additional habitat and probably reduces. competition among epizootic forms. At the moment, information on competition in live bottom habitats is so limited that further investigations concerning growth, successionjand settlement of epifaunal invertebrates appear to be entirely justified. In shallow water marine communities, predation on competitively dominant species by a single dominant predator allows less competitive species to coexist with other members of the community (Connell 1961a, 1961b; Paine 1966; Dayton 1971, 1.975; Porter 1972, 1974) and hence, increases species diversity. In our study, few numerically dominant or common species were consumed by fishes which suggests that predation may not be an important mechanism for explaining the high diversity of live bottom fauna. Although we have not extensively examined trophic. level dynamics within the live bottom community, there is currently no evidence which suggests that the species inhabiting these areas are under heavy predation pressure. Diversity values did not exhibit any discernible patterns with regard to depth or latitude at stations sampled south of Cape Fear. The high number of species; collected at outer shelf stations OS03 and OS01 by dredge and trawl was not consistent from one sampling period to the next. Furthermore, not all collections taken within a sampling period at these stations had unusually large numbers of species. Apparently, all hard bottom areas sampled during the current study were sufficiently similar to preclude any obvious differences in diversity between areas. Bottom temperature differences were much more pronounced between winter and summer at the inner shelf stations than at the middle or outer shelf sites (see Chapter 3), but the observed variations in 144 temperature and other hydrographic parameters apparently had little influence on diversity. At stations sampled off North Carolina, the southernmost station in Onslow BaT had higher species diversity than either IS04 or OS04, which were located in more northerly waters (Vol. II, Chapter 5). A comparison of diversity values from summer collections made south of Cape Fear with those made nortU of Cape Fear (Vol. II, Chapter 5, Table 5.11) indicates higher H', SR, and @ vapues for the more southern stations. This may be attributed to more stable _@ydftraphic conditions of waters south of Cape Fear. Although the number of invertebrate taxa collected (1175) was high, we believe it may underestimate the actual number of species collected because many organisms were not identifiable due to damage or undetermined taxonomic status (e.g., Actiniaria, Nematoda, Turbellaria, Entoprocta, Ostracoda). In addition, other macrofaunal taxa were undoubtedly missed during sampling due to the physiographic complexity of the habitat. Community Composition: Assessment of benthic organisms through television, still camera, and diver observations indicates that megafauna contribute significantly to the physical complexity of hard bottom communities on the South Atlantic continental shelf. This was especially evident at the inner shelf sites due to the relatively high incidence of the octocorals Leptogorgi@ virgulata and Titanideum frauenfeldii and the finger sponge Haliclona oculata, combined with the presence of other large sponge and octocoral species such as Ircinia campana, Spheciospongia vespariumP and Lophogorgia hebes (Figures 5.1 and 5.2). Because rock outcroppings @ere scarce at station IS01, these megafaunal species repre- sented the primary source of habitat relief; however, they showed no strong distributional patterns at this site. At the other two inner shelf sites (IS02 and IS03), the distribution of these sponges and octocorals was patchy and restricted to areas of rock relief or areas of rock with a thin sand veneer. Additional taxa which contributed to relief at inner shelf sites, but which occurred only infrequently, included the stony corals Oculina spp. and Solenastrea hyades, and algae. Although the incidence of some octocorals (Leptogorgia virgulata, Lophogorgia hebes) and sponges (Haliclona oculata) was lower at middle shelf stations (Figures 5.1 and 5.2), physical complexity of the community due to megafaunal species was still very apparent. The sponges, Ircinia campana and Spheciospongia vesparium, were the largest species observed and were most frequently located on or near ledges. Titanideum frauenfeldii was the most frequently occurring octocoral at middle shelf sites, although Muricea. pendula, L. bebes, and L. virgulata were also present at one or more of the stations. The relative rarity of T. frauenfeldii and I. campana. at MS03 was probably due to the relatively low frequency of hard bottom present at this site (Figure 4.10), rather than to any latitudinal effects. Oculina spp., Solenastrea hyades, and algae were present at most of the middle sh f stations but were infrequent. At station MS04, located north of Cape Fear (Vol. II, Chapter 5), algae were the dominant canopy group; whereas, sponges and octocorals were most important at our middle shelf sites. At outer shelf sites, the lower incidence of sponges and coral noted on television transects suggests that the physical complexity due to biological communities may be reduced in this depth zone. The most common large sponge, Ircinia campana, was usually observed on the top of rock outcroppings, and the increased frequency of this species at OS02 and OS03 may be correlated with 145 the greater number of outcroppings at those stations. Other large sponges and corals were sparse at outer shelf sites, including an antipatharian (Stichopathes sp.) which was only found at this depth zone and at station OS04 off North Carolina. Sponges were not frequently observed on the outer shelf north of Cape Fear (Vol. II, Chapter 5). Instead, the octocorals Titanideum frauenfeldii and Leptogorgi@@ virRulata were most important at this station. The bathymetric patterns of sponges and octocorals detected on our television transects have not been well documented in the literature. Prior television reconnaissance of South Atlantic hard bottom areas (Continental Shelf Associates 1979, U. S. Geological Survey 1979, Powles and Barans 1980, MARMAP unpub. data S@ C. Marine Resources Center, Charleston) has been used primarily to document the location and extent of hard bottom habitats * Obser- vations. on the benthic fauna noted in these reconnaissance efforts are very qualitative and generalized. While our television analysis must also be considered somewhat qualitative due to variations in the height of the tele- vision above bottom, our more intensive analysis of the fauna through segmen- tation of the transects into two-minute intervals provides information useful for predicting megafaunal constituents of hard bottom areas at various depths. Limited quantitative information obtained through analysis of photographic quadrats (Table 5.4) lends support to the distributional patterns noted previously. However, due to the patchy distribution of these species and the small quadrat size utilized (3 m2), many more quadrats must be analyzed in this type of assessment before accurate density estimates of megafaunal taxa can be obtained. Analysis of collections made by dredge and trawl indicated that macro- infaunal assemblages differed according to bathymetric zones. Zonation was most noticeable between assemblages at inner and outer shelf sites. Similar findings were reported for stations sampled off North Carolina (Vol. II, Chapter 5). Although many macrofaunal species were collected at inner shelf sites during both sampling periods, those which were most faithful to these areas included the sponges Spheciospongia vesparium and Homaxinella walton- smithi; the echinoderms Arbacia punctulata and Ocnus pygmaeus; the octocoral Leptogorgia virgulata; t_hetunic@tes Clave-lina picta and Styela plicata; and- the mollusk Diodora cayenensis. Likewise, outer shelf sites were characterized by the echinoderm Eucidaris tribuloides; several bryozoans, including Smittipora levinseni, Cleidochasma porcellanum, Stylopoma informata, Cycloperiella rubra, Membraniporella aragoi, Floridina antiqua, and Para- smittina s_pathulata; and the cnidarian Dynamena dalmasi. Middle shelf live bottom areas are apparently transition zones which support species having both inner and outer shelf affinities. Ordination analysis was particularly useful in pointing out the similarity in species composition between middle shelf sites and inner or outer shelf sites. Most species which were consistent- ly collected at middle shelf stations were also collected at inner and outer shelf sites as well; however, the cnidarians Hebella venusta, Aglaophenia allmani, A. latecarinata, Scandia mutabilis, 9-yn-thecium tubitheca, Sertularia marginata, Hincksella cylindrica, and Thyroscyphus marginatus; and the bryozoans @q@er@ia sp. , Nellia tenella, and Schizoporella f loridana were usually both constant and faithful to middle shelf sites and are representative of live bottom habitats from this area of the shelf. Although many other species were collected at inner, middle, and outer shelf live bottom stations, they tended to be more ubiquitous. 146 Based on faunal composition, station affiliations among site groups varied with sampling period and with the gear utilized. During winter the greatest differences in faunal composition were between inner shelf stations and all others. Zonation was also evident on the continental shelf in summer when maximum dissimilarity occurred between inner and outer shelf stations. IMultivariate techniques also separated quantitative collections of smajer epibenthic and infaunal organisms, sampled by suction and grab, acco ding to bathymetric zones during winter but not during summer. In winter, outer shelf sites were separated from inner and middle shelf sites, whereas no delineation of areas, based on community composition, was evident during summer. Ordination confirmed the results of normal cluster analysis and was useful in pointing out misclassification of collections by cluster analysis. Most of the species collected by suction and grab samplers were found at stations in all three depth zones; however, a few species such as the annelid Pista_quadrilobata, the decapod Pelia mutica, the sponge Homaxinella waltonsmithi, and the mollusk Pteria colymbus were both faithful and constant at inner shelf sites. Similarly, the amphipods Unciola sp. A and Erichthonius sp. A; and the annelids Syllis sp. D, Glycera capitata, Syllis .@ornuta, and Spio pettiboneae were consistently found at outer shelf stations. Analysis; of dredge and trawl collections has shown that the middle shelf areas were composed of species with affinities to inner or outer zones. The only species consistently collected at middle shelf sites during both sampling periods were the sponge Cinachyra ailoclada and the polychaete Syllis alternata. Despite evidence for the existence of faunal zonation patterns related to depth, the point should be made that these apparent trends may actually have been an artifact of sampling methodology which was not consistent over the entire shelf. Thus, grab collections, which were only taken at outer shelf stations and which were restricted to sand or the sand layer on rock, included fewer animals and more infaunal organisms (such as haustoriid amphipods) than did suction samples, which were taken primarily over rock covered by sand. Zonation patterns observed at live bottom stations during winter and suT=er may reflect seasonal fluctuations in the occurrence of many epifaunal inverte- brates. Periods of dormancy among invertebrates in response to critical environ_ mental conditions are well documented in estuarine and nearshore envirorunents. Dormancy has been reported for sponges (Wells et al. 1964), the entoproct Barentsia laxa. (Van Dolah et al. 1979), the phoronid Phoronis hippocepia (Hyman 1959), and hydroids (Morse 1909, Berrill 1948, Tardent 1963, Hargitt 1900, Calder 1967, 1971). In most instances, the dormancy period was initiated in response to water temperatures. Migration of mobile epifauna in response to temperature may also be a factor in determining zonation patterns. Evidence for this was presented by George and Staiger (1977), who noted dynamic seasonal shifts in populations of epifaunal invertebrates. Changes in the community structure of live bottom invertebrates, whether effected by dormancy or movement, are apparently influenced by hydrographic conditions in the South Atlantic Bight. The Gulf Stream is an important determinant of hydrographic conditions on the outer shelf and is especially evident in winter. A warm band of water with relatively constant temperature and salinity is present year-round in the open shelf zone at depths of 33 - 40 m; however, inner and outer shelf waters are subject to considerable s9sonal fluctuations (Mathews and Pashuk 1977). Cerame-Vivas and Gray (196 noted that there is commonly a 100 - 120C difference in bottom temperature between the inner and outer North Carolina shelf waters during winter. Coastal and inner shelf waters are influenced by local seasonal weather conditions and 147 run-off'. In winter, the warmest water is found just inshore of the shelf break and is bounded on both sides by colder water (Mathews and Pashuk 1977). In summer, water temperatures are much more uniform over the entire width of the shelf encompassing our middle and outer shelf stations. Seasonal changes in water temperature on the inner shelf may have influenced zonation patterns observed by forcing inhabitants of this area to migrate or tolerate cold through dormancy, eurythermy, or other adaptive mechanisms during the winter. No latitudinal gradients in species assemblages were noted for any of the inner, middle, or outer shelf zones; however, our stations did not encompass a wide latitudinal area. Latitudinal trends may have been more obvious; if sampling had included sites further south off Florida, such as the shelf edge prominences sampled by Avent et al. (1977). They found that macrofauna dredged from these prominences exhibited an affinity primarily with the Antillean faunal province. Although a thorough analysis of the zoogeography of the taxa from this study is beyond the scope of this report, it appears that live bottom areas below Cape Fear consist mainly of southern (Carolinean and Caribbean) or widespread species. This conclusion agrees with observations by Cerame-Vivas and Gray (1966) who noted that species found at inner to middle shelf depths south of Cape Hatteras were mainly southern, being found between. North Carolina and Florida. Eighty-seven percent of the species in their study from the outer shelf were southern or tropical (Caribbean). At stations IS04 and OS04 sampled off Cape Hatteras, invertebrate assemblages were characteristic of the Virginian Province; however, fauna at station MS04 was typically Carolinean, suggesting that a latitudinal gradient in species assemblages occurs north and south of Cape Hatteras (Vol. II, Chapter 5). Dominance: Characteristic species of macrofaunal invertebrates dominated collections in terms of abundance or frequency of occurrence. Although no attempt has been made in our sampling design to directly contrast species composition between live and sand bottom areas, we know that certain taxa such as sponges, cnidarians, and bryozoans are primarily found on hard bottom substrates. Dominant taxa collected off North Carolina included algae, mollusks, decapods, sponges, and echinoderms (Vol. II, Chapter 5). Examination of the species most frequently collected by dredge and trawl at our stations (Tables 5.5 and 5.6) revealed that most are associated primarily with hard substrates such as live bottom or isolated patches of shell. Species frequently occurring and typical of "reef" areas include 'Lophogorgia hebes, Campanularia hincksii, Clytia fragilis, Celleporar.ia albirostris, Ro'nostaechas quadridens, Turbicellepora dichotoma, Titanideum frauenfeldii, Crisia sp., Thyroscyphus marginatus, Spheciospongia vesparium, Conopea merrilli, and Styela plicata. In contrast, most of the common motile invertebrates, such as decapod crustaceans, polychaetes, amphipods, and echinoderms, are found on a variety of bottom types. Most of the numerically dominant taxa collected by suction and grab are also ubiquitous, with some being found from the intertidal zone to deep oceanic water. The colonial serpulid Filograna im2lexa is cosmopolitan in temperate and tropical seas, occurring from the intertidal zone to > 100 m. Its reported mode of reproduction is by transverse fission (Day 1967). This explains the extremely patchy distribution of this species which was abundant in only a few collections. Phyllochaetopterus socialis, a chaetopterid polychaete which 148 forms branched colonies, occurs from the intertidal zone to > 100 m throughout the Atlantic Ocean (Day 1973). This species is not exclusively associated with live bottom but is generally found on low relief rock covered by a thin sand veneer (Continental Shelf Associates 1979). Spiophanes bombyx was found by Frankenberg and Leiper (1977) to be a numerically dominan t member of the nea. shore fine sand habitat. Its dominance in suction and grab collections was primarily a reflection of its occurrence in samples collected either on san veneer of rocks or from sand patches between rocks. Syllis spongicola occurs in a variety of habitats including those provided by sponges, ascidians, rocks, pilings, clay, sand, silt, and coral. It is found in the intertidal zone and to depths of 400 m (Gardiner 1975). Exogone dispar is also fairly ubiquitous, being found on shell, stone, coral, sand, algal masses, and hydroids. It has the greatest depth range of the numerically abundant poly- chaetes and is found from low water to 5000 m (Gardiner 1975). The caprellid amphipod Luconacia incerta is widely distributed in temperate and tropical areas of the western North Atlantic where it has been reported on Sargassum, ascidians, and octocorals. The ophiuroid Ophiothrix angulata is not restricted to live bottom areas but is common in a variety of communities (McCloskey 1970). This species was also found to be numerically dominant at stations north of Cape Fear where it was most abundant at IS04 (Vol. II, Chapter 5). Krebs (1972) and McCloskey (1970) indicate that species which are considered to be dominant should be ecologically constant as well as abundant. Therefore, a representation of dominance based solely on numerical abundance can be misleading, especially since only the smaller macrofauna quantitatively sampled by suction and grab were enumerated in this study. Dominant species which were abundant and frequently encountered during both seasons of sampling included Spiophanes bombyx, Syllis spongicola, Ophiothrix angulata, and Photis sp. The other numerically dominant species were less constant in their occurrence. In particular, the ecological significance of dominance by the colonial species Filograna implexa and Phyllochaetopterus socialis cannot readily be assessed because of their highly contagious distribution. These species are probably important, however, because they provide additional substrate and microhabitats for other species. Biomass: Biomass data from the current study can be loosely compared with that reported by George and Staiger (1978) in their study of epifaunal invertebrates collected by trawl from the South Atlantic Bight. During both winter and summer, the biomass of invertebrates from our live bottom trawl collections greatly exceeded the values reported by George and Staiger (1978) from sand habitats; however, at the three "reef-type" stations sampled, they found the biomass of sponges, tunicates, and soft corals to be extremely high. These results contrast with those from stations sampled off North Carolina where scleractinians, mollusks, and algae were dominant (Vol. II, Chapter 5). Our data indicated no significant difference in biomass between winter and summer (Tables 5.9 and 5.10). This is not surprising considering the sessile nature of most of the major macrofaunal taxa. Any variations which were noted in biomass were probably a result of the patchy distribution of the attached epifauna. Sponges were the main contributors to the large biomass estimates for live bottom areas sampled in this study. Although seasonality is probably exhibited by cnidarians, bryozoans, ascidians, and smaller sponges, the large sponges such as �pheciospongia vesparium and Ircinia campana probably 149 are several years old and do not fluctuate in abundance or biomass as a result of seasonal influences. No noticeable bathymetric trends in biomass of macrofauna were noted for dredge collections. For trawl collections, we found that biomass was low during both sampling periods at OS01, the only outer shelf station sampled, and at station MS02 during summer. As noted from the analysis of videotapes, the frequency of the large sponges appeared to decrease at the outer shelf stations. Biomass of macroinvertebrates was low at station MS02 during summer because only one small (2.5 kg) S. vesparium was collected. The infrequent capture! of sponges at this station during simmer was also reflected by their lower frequency of occurrence in television transects in summer. IMPACT/ ENHANCEMENT The analysis of benthic communities presented in this chapter is primarily intended to provide information on the composition and structure of communities associated with hard bottom habitats in different areas of the South Atlantic Bight. A direct assessment of impacts on these communities from drilling operations is not possible since the study areas have not been influenced by energy related activities. However, several potential impacts should be noted. The discharge of drilling fluids and cuttings from oil rigs increases sedimentation in the near vicinity of the platform. If this discharge occurred over live bottom, possible consequences for the biota include: (1) smothering of sessile invertebrates, particularly smaller colonies, or inhibition of filter feeding; (2) altered community structure due to decreased hard substrate availability; (3) burial of infauna inhabiting the sand in the vicinity of rock outcroppings; and (4) decreased algal growth due to increased turbidity. Of these consequences, (1) and (2) would probably have the most severe impact on live bottom communities in our study area since sessile fauna (sponges, corals, ascidians, hydroids, bryozoans, etc.) represent the major invertebrate component in terms of biomass, and they are extremely important in providing structurally complex. microhabitats for smaller macrofauna. Unfortunately, very little is known concerning the tolerance of sessile fauna to increased sediment load. Thus, it is not possible to predict whether moderate increases in sedi- mentation, which may not result in burial, would be detrimental to these organisms; nor can we predict the rate of recolonization and recovery to former levels of abundance and biomass for species characteristic of South Atlantic Bight live bottom areas. The smaller sessile biota, such as ascidians, bryozoans, hydroids, small sponges, and some octocorals, may recolonize and grow relatively rapidly as has been observed in other studies (Jackson 1977, Parker et al. 1979, Marine Resources Research Institute 1979); however, larger sponges and octocorals may exhibit comparatively slow growth rates. Data on recolonization and growth rates are sorely needed. The severity of the impact of discharging drilling muds and cuttings on these habitats is dependent on distance of the drilling operations from live bottom, duration of plume presence, current patterns, water depth, and location of discharge source relative to the bottom. In shallow shelf areas, locating the discharge point 11v 10 m below the surface, as required by federal regula- tions (U. S. Department of the Interior 1981), might result in a more severe concentration of sediments in a localized area due to bottom proximity and slower currents, whereas applying this same strategy in deeper shelf waters would largely dilute and disperse the discharge plume over a much greater area. 150 Negative impacts from plume discharge on smaller infauna and algae might not be as severe as the impacts on sessile colonial invertebrates. Bender et al. (1979) reanalyzed benthic biological data (including macroinfauna) from waters off Louisiana and found no "indication of a stressed environment near or aroundloil drilling and production platforms." The potential impact on macrralgae is probably minimal since they were generally not prevalent at our Stu areas. I The detrimental factors related to plume discharge are generally restricted to the vicinity of the discharge point (< 1000 m, Ecomar Inc. 1980). Thus, placement of oil rigs or discharge points at least 1000 m from live bottom areas, combined with the current lease sale stipulations (U. S. Department of the Interior 1981), should lessen or avoid detrimental effects related to drilling muds and cuttings. Other potential detrimental effects from drilling operations include those related to oil spills or gas leaks. Bright (1977) observed no large scale disturbance on live bottom fauna by methane seeps, suggesting that gas leaks from platform operations may not severely affect live bottom communities. Previous studies on the effects of oil spills have been largely restricted to laboratory toxicity studies and field investigations of infaunal communities, particularly in semi-enclosed intertidal and shallow subtidal areas (Sanders 1978, Thomas 1973, Blumer et al. 1971, Foster et al. 1971, Nicholson and Climberg 1971). At the organismal level, petroleum hydrocarbons have been demonstrated to cause direct lethal toxicity as well as sublethal disruption of physiological and behavioral activities (Moore and Dwyer 1974). At the population and community levels, ecological imbalances may result from the elimination of key species,e.g., predators or grazers (Boesch and Hershner 1974), or from habitat changes effected by alterations in the physical or chemical environment (Moore and Dwyer 1974); however, some studies suggest that infaunal abundances may actually increase in response to low level chronic exposure to petroleum hydrocarbons in the vicinity of a natural oil seep (Spies and Davis 1979, Davis and Spies 1980). Specific evidence for detrimental effects of oil spills on live bottom which it was observed that some corals, especially "branching varieties," are communities is sparse; however, Boesch and Hershner (1974) cite one study in severely damaged if coated by oil while exposed to air. The implications of this finding for submerged live bottom fauna are unclear, however. It was suggested that individual polyps may be afforded some degree of protection from direct contact with oil by virtue of the copious amounts of mucous they secrete; however, the porous limestone of some scleractinian corals may actually absorb and concentrate oil from the aqueous milieu. Similarly, sponges may have analogous capabilities, although this is purely conjectural. Whether or not any of these effects impact live bottom communities in the vicinity of an oil spill is currently a moot point in the absence of sufficient information concerning either the fate of oil spills in the open ocean environ- ment or the sensitivity of live bottom fauna to oil contamination. Furthermore, an accurate assessment of the potential impacts from an oil spill would depend upon a consideration of the synergistic or antagonistic effects of-water temperature, dissolved oxygen concentration, and life stage of the individual organisms influenced by the spill. Enhancement effects related to oil platform operations result fLm the creation of artificial reefs by the addition of hard substrate. Colonization of platforms would probably be rapid, and the subsequent fouling community of invertebrates and algae would, in turn, attract many fish, as noted by others 151 (U. S. Department of the Interior 1981). Live bottom fauna would contribute to the colonization as a source of recruitment, but distance between live bottom areas and platforms should not be a factor since most sessile biota produce planktonic larvae or spores which are widespread throughout the South Atlantic Bight. CONCLUSIONS A total of 1175 identifiable taxa of invertebrates was collected with all sampling devices during winter and summer. Comparison of number of species with the literature indicates that the live bottom areas studied are more diverse than the surrounding sand biotope. As indicated by dominance diver- sity curves, a large number of uncommon or rare species contributed to the high diversity of live bottom areas both south and north of Cape Fear, N. C. The values of H', which ranged from 1.43 bits per individual at IS02 in summer to 6.63 bits per individual at IS03 in summer, were generally similar between stations for both sampling periods. Low H' values were associated with high abundance of invertebrates but low evenness. Species richness values were similar between stations and sampling periods, but numbers of species and individuals were different between stations during winter and summer. Among; macrofauna collected by dredge and trawl, the Bryozoa, Cnidaria, and Porifera were dominant, whereas the Annelida and Mollusca were most important in terms of number of species in collections made by suction and grab. At stations off North Carolina, algae, mollusks, decapods, sponges, and echino- derms were dominant taxa. Composition of the major invertebrate groups represented in dredge collections did not differ appreciabiv between inner, middle, and outer shelf stations. In collections made by trawl, the Porifera was a dominant component only at inner shelf stations, while the Cnidaria and Bryozoa were important at stations sampled on the middle and outer shelf. Remote sensing of megafauna suggested that frequency of occurrence of the large sponges (especially Haliclona oculata) and octocorals (especially Leptogorgia virgulata) at live bottom sites decreases with increasing depth. Macroalgae were not frequently collected by any sampling gear at stations south of Cape Fear; however, they were very important at mid-shelf depths off North Carolina. Biomass determinations of the larger invertebrates collected at most live bottom sites by dredge and trawl showed that sponges were dominant during both winter and summer. Off North Carolina, the biomass of algae, sclerac- tinia.ns, and mollusks exceeded that of other taxa. No difference existed in biomass estimates between winter and summer, but spatial differences in bioma.ss estimates based on trawl collections were present. The low biomass values found at OS01 may reflect decreased occurrence of large sponges at outer shelf stations. Species composition was generally distinguishable based on the depth of the live bottom sites examined. Although species assemblages were not always restricted to live bottom sites in particular depth zones, certain species were most consistently collected at inner, middle, or outer shelf stations. 152 Most species associations varied from one sampling period to the next, suggesting that seasonality may be important. Faunal differences were most evident between inner and outer shelf live bottom communities, while the middle shelf appeared to be an area of transition. This zonation was noted at sites north and south of Cape Fear. Unfortunately, differences in sampling M hodology between depth zones limits conclusions which can be made on fpnal zonation. No latitudinal gradients in species assemblages were noted t r stations south of Cape Fear, possibly due to the narrow range'of latitudes included in this study; however, inner and outer shelf stations off North Carolina contained many species characteristic of the Virginian province, indicating penetration of temperate species below Cape Hatteras. Numerically dominant invertebrates collected by suction and grab samplers were patchily distributed. Because of the highly contagious distribution of most species, the current number of replicates was inadequate to assess changes in population densities with any degree of confidence. The ranking of numerically dominant species changed considerably from winter to summer, and differences in numerical dominance also existed between bathymetric zones. The potential impact of drilling fluids and cuttings from oil rigs would include increased sedimentation in the vicinity of the platform. Other adverse effects from discharge could include altered community structure due to decreased availability of hard substrate, and smothering of sessile invertebrates which represent the major biological component in terms of biomass. Negative impacts from plume discharge on smaller infauna. and algae might not be as severe as the potential impacts on sessile colonial inverte- brates. Any detrimental effects related to oil and gas activities should be lessened if discharge points are placed at least 1000 m from live bottom areas, and if other current lease stipulations are observed. Enhancement effects related to oil platform operations may result from the addition of hard substrata, which creates artificial reefs. 153 CHAPTER 6 NEKTONIC COMMUNITY INTRODUCTION At present thiere is little quantitative data on distribution and abundance of demersal fishes associated with live bottom in the South Atlantic Bight. In an extensive study of shelf fishes of the Bight, Struhsaker (1969) reported the results of exploratory groundfish trawling and described live bottom and its associated fish fauna. Although the National Marine Fisheries Service (NMFS) Marine Resources Monitoring and Assessment Program (MARMAP) has conducted extensive groundfish monitoring.with trawl collections (Wenner et al. 1980), published reports have been limited to coastal, open shelf, shelf edge, and lower shelf habitats. George and Staiger (1978) described fish assemblages in the Bight from trawl collections, but most collections were over areas of sand bottom on the open shelf. Miller and Richards (1979) examined trawl logs from several exploratory fishing vessels and categorized live bottom areas based on depth, thermal stability, and indicator reef species; however, they provided little quantitative data on abundance of these and other live bottom species. Powles and Barans (1980) tested the effectiveness of trawls, traps, diver observations, and underwater television as sampling methods for live bottom fishes and gave biomass estimates for some species. The purpose of the present study is to provide quantitative and qualitative data on the distribution, abundance, diversity, and community structure of demersal fishes from several live bottom areas in the South Atlantic Bight and to examine seasonal, latitudinal, and depth related patterns in these parameters. METHODS Laboratory Analysis: Trawl Collections - Fishes preserved from trawl collections (Chapter 2) were washed in tap water and transferred to 50% isopropanol. All unknown specimens were identified and added to data forms for computer entry. Voucher specimens were catalogued for all species collected. Underwater Television Transects - Videotapes from underwater television transects were analyzed in a manner similar to that utilized for invertebrates (Chapter 5). An attempt was made to analyze 60 minutes of videotape at each trawlable site by selecting three 20-min transects which were independent in space and time. At high relief sites which could not be trawled, six 20-min transects, three day and three night, were analyzed. Lengths of transects (m) were measured between start and end Loran C coordinates. Procedures for fish enumeration were as follows: One observer viewed the tapes and counted fish seen on the entire monitor screen for every ten-second interval of tape. A second observer then viewed the same tape and made counts. For time intervals in which the two observers could not agree on the number of fish seen, an average of the two counts was used. For large schools of fish which were! impossible to count, the count was recorded as 100 fish for the ten-second interval in which they occurred. The tape was then viewed a third time by both observers in an attempt to identify fishes which had been counted 154 but not identified during earlier viewings. These attempts were rarely success- ful. Fish counts were summarized as numbers per 100 m of transect and numbers per hour of videotape. Fish density (number of individuals per hectare) was calculated by multiplying the transect length by the estimated horizontal field of view, estimated to be 3.4 m, based on measurements made in a swimming pool. Diver Observations - Abundance of fishes in diver hand held still camera phofographs was calculated as total number per stop. A stop consisted of 4 photographs taken at right angles to each other (see Chapter 2). Abundance of fishes seen on swimming transects was calculated as total number per minute of observation. Baited Fishing Gear - Longlines, snapper reels (hook and line), and traps were deployed primarily to capture large predatory species, which were rarely captured by trawl, for food habits analysis (Chapter 7). 1n addition, these gears provided some qualitative information on demersal fish distribution, and the data from these gears were summarized. Juvenile Fish Sled - All larval and juvenile fish specimens were removed from each epibenthic sled sample and identified to the lowest taxon possible. Larvae of most species remain undescribed, and thus larval specimens were frequently not identifiable beyond the generic or even family level. Specific identification of undescribed larvae was sometimes possible using fin ray counts, if full meristic complements were developed. For each sample, number of individuals per taxon and their minimum and maximum sizes were recorded. Voucher specimens for each taxon were labeled, preserved in 5% buffered formulin, catalogued, and stored in a dark room to preserve pigment characters useful in identification. Data Analysis: Biomass - Fish biomass was calculated as mean catch per tow for the replicate trawls done on each station. Because previous investigations (Taylor 1953, Struhsaker 1969) have shown that trawl catches are usually distributed as a negative binomial, a 10ge (x + 1) transformation was made on the data (Elliott 1977). Mean biomass estimates per tow were calculated for each station from transformed values following the methodology of Bliss (1967): Eff exp(7 + S212)-l h b h th where E(y is the estimated (retransformed) mean catch per tow at the h station; 7h and Sh expressed in logarithmic units, are the mean biomass per tow and its variance for the hth station. Biomass was also calculated as kg of fish ha-l of area swept'by the trawl. Area swept by the trawl (a) was determined for each collection by the following equation modified from Klima (1976): a D(O.6H) 10,000 h@ZT I where D = bottom distance in metres covered by the trawl, as calculated from- start and end Loran C coordinates, and H is the trawl headrope length in metres. The constant 0.6 designates an effective horizontal trawl opening of about 60% of the headrope length as used by Roe (1969) and established by Wathne (1959). 155 The average swept area of our trawl for all stations was estimated to be 4.3 ha tow-1. Because large elasmobranchs such as Dasyatis spp. and Ginglymostoma cirratua@, and large catches of schooling pelagic fishes, such as Decapterus punctat.s, contribute significantly to the variance in trawl catches, biomass was calculated on demersal teleosts alone as well as on total nekton (all fishes and squid). 4 Abundance -IAn index of relative abundance (Musick and McEachran 1972) was calculated by station for each dominant species and for total demersal teleosts as follows: Index of Relative Abundance Z loge (X + 1) n where n is the number of trawls at a station and x is the number of individuals in each tow at that station. This index was calculated for the ten species which were most abundant over all stations and seasons. Abundance was also calculated for several non-dominant species which were considered priority species because of their commercial and recreational importance. Numerical Classification - Numerical classification techniques were used to compare the similarity between trawl collections (normal analysis) and to elucidate species assemblages (inverse analysis). To reduce the effect of contagion generally present in trawl collections (Taylor 1953), the data were transformed [loglo (x + 1)] before analysis. To prevent the chance occurrence of rare species from confusing the results, only species that occurred in three or more trawl collections were included in the analysis. Similarity be- tween collections and between the distribution of species was measured using the Bray-Curtis measure (Bray and Curtis 1957). This is a measure of dissimilarity, and the complement is used to yield a similarity measure (Clifford and Stephenson 1975). The Bray-Curtis similarity measure is expressed as: Sjk i I Xi i - x1ri (x] + X ii ki where Sjk is the similarity between entities j and k 'xji is the abundance of the ith attribute for entity j, and xki is the abundance of the ith attribute for entity k. In normal analysis (Clustering by collection), x is the abundance of species i in collections j and k. In inverse analysis (clustering by species), x is the abundance of species j and k in collection i. Similarity matrices produced by this measure were expressed in the form of dendrograms generated using a flexible sorting strategy (Lance and Williams 1967a, Clifford and Stephenson 1975), with @ = -0.25. Subsequent to cluster analysis, species groups were chosen from the inverse classification by utilizing a variable stopping rule (Boesch 1977). Nodal analysis was then used to determine the constancy and fidelity of each species group to I the seven trawlable stations. Constancy is a measure of the frequency of occur- rence of a species group among all samples at a station, and fidelity is an expression of the constancy of a species group to collections at one station over all collections at all stations (Boesch 1977). Constancy is equal to 1 when all species in a group occur in all collections at a station and zero when no species 156 in a group occur in any collections at a station. Fidelity is equal to 1 when the constancy of a species group at a station is equal to its overall constancy, greater than 1 when constancy at a station is greater than its overall constancy, and less than 1 when its constancy at a station is less than its overall con- stancy (Boesch 1977). Constancy and fidelity were compared between species groups and collections from fixed stations for each season. ' Dominance and Diversity - The fish community of each station was characterized by its numerically dominant species from trawl catches. Dominant species were considered to be the ten most abundant species at each station. The degree of community dominance by abundant species at each station was expressed in dominance diversity curves (Whittaker 1965) and by a dominance index (McNaughton 1967) expressed as follows: DI = nl + n2 (100) N where n, and n2 are the numbers of individuals of the first and second most abundant species, and N is the total number of individuals. After removal of pelagic fishes and squids, diversity was calculated for demersal fishes for each tow and for pooled collections at each site by H' and its components, species richness and evenness, V(Pielou 1975). Diversity indices were' also calculated for collections pooled by day or night for each site. Collections were pooled in order to more accurately assess diversity at each site based on repeated sampling of the community. RESULTS Quantitative Assessment of Fish Captured by Trawl: Species Composition and Abundance - A total of 62,840 fishes representing 54 families, 98 genera, and 128 species were taken in 83 trawl collections during both seasons. Of these, 50,771 belonged to the demersal fish community and the remaining pelagics were mainly carangids and clupeids (Appendix 14). Of the demersal fishes, ten species made up 94.2% of the total number of individuals and the two most abundant species, Stenotomus aculeatus (30,714 individuals) and Haemulon aurolineatum (8916 individuals) made up 78.1% of the total. Other abundant species were Rhomboplites aurorubens (4748), Equetus lanceolatus (761), Centropristis striata (582), Prionotus carolinus (484), Calamus leucosteus (475), Equetus umbrosus (458), Urophycis regia (374) and Monacanthus hispidus (335). Stenotomus aculeatus, H. aurolineat -_ and.R. aurorubens were the most abundant species in both winter and su er; however, other dominant species varied in community ranking seasonally (Table 6.1). Major seasonal differences included increased abundance of C. striata during the summer and the appearance in summer of large numbers of Apogon p6eudomaculatus, which were absent in winter. Equetus lanceolatus, which was very abundant in winter, was rarely captured in the summer Urophycis regia was common in winter but was not collected in summer. Ranking of dominant species changed not only seasonally, but also by station within a season (Tables 6.2 and 6.3). The southern porgy, Stenotomus aculeatus, was generally more abundant in summer than in winter (Figure 6.1) and was the most abundant species at all stations, except OS01, in summer. 157 Table 15.1. Ten most abundant demersal fish species in winter and summer 1980, all stations combined. n = number of occurrences in 42 trawls in winter and number of occurrences in 41 trawls in summer. Total Percent Species Number of Total n WINTER Stenotomus aculeatus 12281 52.0 33 Haemulon aurolineatum 4516 19.1 11 Rhomboplites aurorubens 3540 15.0 19 Equetu3 lanceolatus 738 3.1 10 Urophycis regia 374 1.6 14 Lagodoi rhomboides 275 1.2 10 Calamus leucosteus 265 1.1 23 EquetUS umbrosus 222 0.9 11 Prionotus carolinus 166 0.7 5 Diplectrum formosum 133 0.6 22 SUMIER Stenotomus aculeatus 18433 67.8 37 Haemulon aurolineatum 4400 16.2 31 Rhombo)lites aurorubens 1208 4.4 24 Centropristis striata 462 1.7 26 'Prionotus carolinus 318 1.2 10 Apogon pseudomaculatus 312 1.2 17 Monacanthus hispidus 261 1.0 25 Equetus umbrosus 236 0.9 17 Calamus leucosteus 210 0.8 25 Centropristis ocyurus 154 0.6 21 158 Table 6.2. Ten most abundant demersal fish species, in winter 1980, by station. n - number of occurrences in six replicate trawls. Total Percent of Total Station Species Number at Station n T'Sol Urophycis regia 319 40.1 3 Stenotomus aculeatus 177 22.3 5 Prionotus carolinus 164 20.6 3 Prionotus sp. 23 2.9 1 Centropristis striata 22 2.8 3 Syacium papillosum 19 2.4 3 Urophycis sp. 13 1.6 1 Centropristis.ocyurus 10 1.3 3 Synodus foetens 6 0.8 4 Ophidion holbrooki 4 0.5 2 IS02 Stenotomus aculeatus 174 45.8 5 Lagodon rhomboides 78 20.5 1 Centropristis striata 22 5.8 4 Equetus umbrosus 20 5.3 2 Urophycis re 1 17 4.5 2 &ia Calamus leucosteus 17 4.5 3 Urophycis sp. 11 2.9 2 Syacium papillosum 8 2.1 2 Synodus foetens 6 1.6 4 Ophidion holbrooki 3 0.8 2 IS03 Haemulon aurolineatum 1530 43.2 3 Rhomboplites aurorubens 934 26.4 3 Stenotomus aculeatus 472 13.3 6 Equetus umbrosus 175 5.0 3 Lagodon rhomboides 168 4.8 5 Synodus foetens 35 1.0 6 Orthopristis chrysoptera 30 0.8 3 Centropristis striata 29 0.8 4 Calamus leucosteus 24 0.7 3 Ophidion holbrooki 22 0.6 3 159 Table 6.2 (Continued) Total Percent of Total Station Species Number at Station n msol Stenotomus aculeatus 1163 53.3 2 Haemulon aurolineatum 859 39.4 2 Calamus leucosteus 56 2.6 3 Synodus foetens 15 0.7 6 Diplectrum formosum 12 0.6 3 Lutjanus campechanus 8 0.4 1 Equetus umbrosus 8 0.4 1 Syacium papillosum 8 0.4 3 Aluterus schoepfi 8 0.4 3 Rhomboplites aurorubens 6 0.3 4 MS02 Stenotomus aculeatus 9559 89.4 6 Equetus lanceolatus 621 5.8 4 Rhomboplites aurorubens 138 1.3 3 Calamus leucosteus 89 0.8 6 Centropristis striata 38 0.4 5 Monacanthus hispidis 33 0.3 5 Diplectrum formosum 32 0.3 6 Aluterus schoepfi 31 0.3 4 Lactophrys quadricornis 24 0.2 5 Pagrus pagrus 18 0.2 5 MS03 Rhomboplites aurorubens 2449 42.2 6 Haemulon aurolineatum 2127 36.6 6 Stenotomus aculeatus 735 12.6 6 Equetus lanceolatus 115 2.0 4 Diplectrum formosum 70 1.2 6 Calamus leucosteus 53 0.9 5 Lagodon rhomboides 28 0.5 3 Monacanthus hispidis 28 0.5 5 Centropristis ocyurus 27 0.5 4 Mullus auratus 21 0.4 1 160 Table 6.2 (Continued) Total Percent of Total Station Species Number at-Station n Osol Pagrus pagrus 63 30.9 1 Synodus poeyi 38 18.6 3 Calamus leucosteus 26 12.8 3 Syacium papillosum 22 10.8 3 Urophycis regia 18 8.8 3 Rhomboplites aurorubens 13 6.4 3 Centropristis ocyurus 5 2.4 3 Synodus foetens 3 1.5 1 Equetus (- Pareques sp. nov. 3 1.5 2 Serranus phoebe 2 1.0 2 161 Table 6.3. Ten most abundant demersal fish species, in summer 1980, by station. n = number of occurrences in six replicate trawls (five at IS03). Total Percent of Total Station Species Number at Station n Isol 9tenotomus aculeatus 2942 71.2 6 Haemulon aurolineatum 435 10.5 6 Centropristis striata 194 4.7 6 Monacanthus hispidus 141 3.4 6 Prionotus carolinus 120 2.9 4 Porichthys plectrodo 60 1.4 3 Diplectrum formosum 51 1.2 3 Calamus leucosteus 38 0.9 5 Centropristis ocyurus 30 0.7 3 Apogon pseudomaculatus 25 0.6 3 IS02 Stenotomus aculeatus 2721 53.4 6 Haemulon aurolineatum 1587 31.2 4 Prionotus carolinus 187 3.7 3 Centropristis striata 161 3.2 5 Apogon pseudomaculatus 59 1.2 3 Syacium papillosum 57 1.1 3 Monacanthus hispidus 40 0.8 5 Diplectrum formosum 40 0.8 3 Porichthys plectrodon 33 0.6 3 ScorpaeLla brasiliensis 26 0.5 3 IS03 Stenotomus aculeatus 1730 58.2 5 Haemulon aurolineatum 921 31.0 4 Centropristis striata 60 2.0 4 Calamus leucosteus 33 1.1 2 Monacanthus hispidus 32 1.1 4 Equetus umbrosus 30 1.0 2 Lagodon rhomboides 20 0.7 4 Porichthys plectrodo 20 0.7 1 Rhomboplites aurorubens 15 0.5 2 Orthopristis chrysoptera 14 0.5 2 162 Table 6.3 (Continued) Total Percent of Total Station Species Number at Station n HS01 Stenotomus aculeatus 1443 46.9 6 Haemulon aurolineatum 799 26.0 5 Rhomboplites aurorubens 399 13.0 6 Apogon pseudomaculatus 163 5.3 3 Centropristis ocyurus 48 1.6 3 Ophidion holbrooki 48 1.6 2 Calamus leucosteus 31 1.0 5 Diplectrum formosum 26 0.8 5 Monacanthus hispidus 19 0.6 3 Aluterus schoepfi 11 0.4 3 MS02 Stenotomus aculeatus 8580 88.1 6 Haemulon aurolineatum 479 4.9 6 Rhomboplites aurorubens 460 4.7 6 Calamus leucosteus 52 0.; 6 Centropristis striata 33 0.3 5 Apogon pseudomaculatus 18 0.2 3 Monacanthus hispidus 18 0.2 5 Ophidion holbrooki 14 0.1 3 Priacanthus arenatus 10 0.1 4 Prionotus carolinus 10 0.1 2 MS03 Stenotomus aculeatus 1015 62.2 6 Rhomboplites aurorubens 192 11.8 5 Haemulon aurolineatum 179 11.0 6 Apogon pseudomaculatus 38 2.3 3 Equetus umbrosus 26 1.6 3 Aluterus schoepfi 24 1.5 4 Centropristis ocyurus 16 1.0 4 Porichthys plectrodon 16 1.0, 3 Equetus lanceolatus 15 0.9 2 Ophidion holbrooki 13 0.8 3 163 Table 6.; (Continued) Total Percent of Total Station Species Number at Station n Osol Equetus umbrosus 145 27.6 3 Rhomboplites aurorubens 141 26.9 4 Calamus leucosteus 53 10.1 4 Serranus phoebe 52 9.9 4 Centropristis ocyurus 22 4.2 - 3 Equetus (- Pareques) sp. nov. 17 3.2 3 Pagrus pagrus 14 2.7 5 Synodus poeyi 13 2.5 3 Scorpaena calcarata 10 1.9 3 Apogon pseudomaculatus 9 1.7 2 -n U3 OD-- ro Iw (D M CD fi.. @ 0 00 cr to 'o, z z cl. Z:l rD -0 0 -h r m rn 0 ......... Wiw* ci) U) 10 (D f\)0 0 cl) (1) INDEX OF ABUNDANCE 0 0 0 0 z1o t)0 0 0 ? 1 0 OD --o WINTER 0 CA 33 Q3 PSUMMER v 9 Jo, I'S @ @lt (D 13) CL low, so Oa I" 165 In winter, S. aculeatus was one of the three most abundant species at all stations except OSOl_._ Southern porgy were most abundant at MS02 and least abundant at OSO1. Most individuals were captured during the day in both winter and slimmer (Table 6.4). Tonitate, Haemulon aurolineatum, were more abundant during summer rather than winter at all stations except MS03 (Figure 6.2). In winter, H. aurolineatum was taken only al IS03, MS01, and MS03 with peak abundance at MS03. Tomtate were absent at MS02 in winter but were abundant there during the summer. In summer, tomtate were abundant at all stations except OS01 and were the second most abundant: species at most other stations (Table 6.3). Most individuals were captured at night in both winter and summer (Table 6.4). Vermilion snapper, Rhomboplites aurorubens., a priority species, were most abundant: at middle shelf stations with no apparent seasonal pattern (Figure 6.3). They were generally not abundant at inner shelf stations, with the exception of IS03, where they were the second most abundant species in winter (Table 6.2). Rhombop.ites aurorubens was the most abundant species at MS03 in winter and was the second most abundant species collected at that site in summer. This species was common at OS01, especially in summer. Vermilion snapper were equally abundant: in day and night trawls in winter but were more abundant in day trawls in summer (Table 6.4). Jackknife fish, Equetus lanceolatus, were common only at middle shelf stations; (Figure 6.4). In winter, they were abundant at MS02 and MS03, and a few weret taken at IS03. In summer, a few were taken at inner and middle shelf stations. None were taken at OS01 during either season. In winter, most jack- knife fish were captured during the day; however, the few that were taken during summer were all caught at night. Black sea bass, Centropristis striata,, a priority species, were caught in the trawl at all stations except 0 01 during winter and summer (Figure 6.5). Catches at inner shelf stations were consistently higher during summer, but not at middle shelf stations. Overall, abundance for this species was highest at inner shelf stations during summer. Abundance was also high at MS02 during both seasons. Most black sea bass were caught at night. Northern searobin, Prionotus carolinus, were most abundant at the two northern inner shelf stations (Figure 6.6) and were frequently a dominant species (Tables 6.2 and 6.3). No clear seasonal abundance pattern was evident. Northern, searobin were common at IS02 in summer, although they were not taken there in winter. All but one specimen were caught at night. Whitebone porgy, Calamus leucosteus, were caught at all stations and., with the exception of IS01 in winter, were collected at each station during both seasons (Figure 6.7). Abundance was highest at middle shelf stations, especially in winter. Whitebone porgy were more abundant in day trawls. The cubbyu, Equetus umbrosus, was occasionally captured at all trawlable stations and was sometimes a dominant species (Figure 6.8). Although it was not captured during winter at the outer shelf station, it was the most abundant species there in summer. All specimens of this species were captured at night. Spotted hake, Urophycis regia, were only collected in winter and were most abundant on the inner shelf, especially at IS01 (Figure 6.9) where it dominated the catch. All but one specimen were taken at night. Planehead filefish, Monacanthus hispidus, were collected at all stations except OS01 and were occasionally aKundant (Figure 6.10). At inner shelf Table 6.4. Abundance of dominant and priority species by season and light phase. n/N represents the ratio of the number of occurrences of each species (n) to the total number of collections (N). Total Number Mean Number per Tow n/N Winter Summer Winter Summer Winter Summer Day Night Day Night Day Night Day Night Day Night Day Night Stenotomus aculeatus 8670 3611 11689 6744 412.86 171.95 556.62 337.20 14/21 19/21 18/21 19/20 Haemulon aurolineatum 2068 2448 1107 3293 98.48 116.57 52.71 164.65 3/21 8/21 14/21 17/20 Rhomboplites aurorubens 1849 1691 880 328 88.05 80.52 41.90 16.40 5/21 14/21 10121 14/20 Equetus lanceolatus 723 15 0 23 34.43 0.71 0.00 1.15 3/21 7/21 0/21 9/20 Centropristis striata 16 104 23 439 0.76 4.95 1.10 21.95 7/21 15/21 10/21 16/20 Prionotus carollnus 0 166 1 317 0.00 7.90 0.05 15.85 0/21 5/21 1121 9/20 Calamus leucosteus 215 50 158 52 10.24 2.38 7.52 2.60 14/21 9/21 13/21 12/20 Equetus umbrosus 0 222 0 236 0.00 10.57 0.00 11.80 0/21 11/21 0/21 17/20 Urophycis _Le.&ia 1 373 0 0 0.05 17.76 0.00 0.00 1/21 13/21 0/21 0/20 Monacanthus hispidus 17 57 15 246 0.81 2.71 0.71 12.30 6/21 13/21 10/21 15/20 Lutjanue campechanus 19 5 1 8 0.90 0.24 0.05 0.40 4/21 3/21 1/21 5/20 Mycteroperca microlepis 2 0 2 1 0.10 0.00 0.10 0.05 2/21 0/21 2/21 1/20 Pagrus pagrus 89 5 18 10 4.24 0.24 0.86 0.50 6/21 2121 5/21 3/20 me lo too (D F, (A M c (D Lw 0 ca tD 0) Al 40. 0010, z 0. Z. CL ;K co z .0 (D CV, 0 rn r 3: rn 13) cn 0 0 Cl) r\) jol. 0 l- ot Im t 1 1 141 U) 0 (n I\) 01 0 0 C+ 19 0 r- 0 0 r.: 0 0 (1) U) INDEX OF ABUNDANC 0 0 0 N 0 0 0 0 CD C3 3 WINTER U3 SUMMER (is 0 168 800 South 'Carolina Rhomboplifes ourorubens 5.0 W -cc 4.0 z 3.0 2.0- W LL x 1.0 1Aj V) number of occurrences "CHARLESTON"-. N number of samples 30 61SOI 6 6 AVANN 82- MS02 OMS01 60SOI 6 Geor a 520 .2 0 6 6 OS02 OIS02 BRUNS I'C'K M S03 T OS03 S03 JACKSONVILLE' 80* Figure 6.3., Relative abundance of Rhomboplites aurorubens during winter and summer, 1980. 169 340 800 South Carolina Equetus lanceolotus .@340 ?.0 0 z X 0 1.0 W z 0.0a number of n occurrences -CHARLESTOk-. number of samples 41sol 2 0 0 S VANN Msol 820 MSOz *OSOI Georgia 320 10 -1764, OIS02 OS02 BRUN ICK MS03 OS03 OIS03 JAC\KS.ONVILLE.' 82' 800 L V Fiaure 6.4. Relative abundance of Equetus lanceolatus during winter and summer, 1980. 4\0 170 340 Soo South Carolina L) 4.0 z M Cc tL 0- jw U. zx x 0.0- z 6 number of n occurrences 7 number of T samples OISOI 320-- V S. ANNAH .2.2 616 &01 0 MS02 OOSOI T Georgia 320 *OS02 S02 3 6- B UN ItK MS03 OS05 IS03 A ONVILLE Sze\' 800 .7 Figure 6.5. Relative abundance of Centropristis striata during winter and summer, 1980. 171 34* 800 South Carolina PrIonotas corolinus @-34* W V 2.0 0 z 191.0 W z ::.Vw.. 0.01 3 4 number of occurrences CHARLESToN N number of samples ISO[ 320-@ 0 0 SAVANNAH 6 6 OMSOI 820 3 OMS02 60SOI T Georgia <32* OIS02 OS02 BRUNSWICK .2.2 616 MS03 0 0 OIS03 OS03 JAC\KISONVILLE.'..' 800 Fia 6.6. Relative abundance of Prionotus carolinus during winter and summr, 1980. c ID G) CD (D 0 UD ko In) 00 cr c: z C@L A 0 z < 4 0 r L.Lj its 0 z Ln 0 (A 10,10 0 0(j) (n 0 r\3 0 0 C+ H F-= m 0 c 0 (A - cx 14A 0 00 0 U) (1) (1) :3 0 0 0 z1o INDEX OF ABUNDANCE ()j r\) 0 0 0 0 OD I I I I I . I 33 c3 WINTER m SUMMER C+ mm"m "mm m MON m m Fo to rD Us 00 W C3 C+ < (D I W ;o 40 @A z z CL oj Z-1 ::o (D 0 fwl r rri rn U) rD Cl+ MICA UJI Lj_j cr MICA 0 0 (J) 0 0 rL MI- oll 0 0 ch U) L93 0 0 0 zl- INDEX OF ABUNDAN 0 0 1 0 0 co WINTER 3 SUMMER C+ i (D CL V) rD 00 rD 0 w W ;a .*... cr c: CL z 4. z 3: 0 r rn 0 mlic < 0 Io CA 010 cl) 0 0 .10 W X 0 0 0 INDEX OF ABUNDANCE 041 N 0 7- !@ w 0 0 0 0 (D I I I I I I I C.+ 0 MWINTER 0 8,33 m 3cr -So SUMMER -T, (D (A 0 w N . I. Cl) ILO a) C= 00 17 z @-lrs Z:. CL IV z (D 0 r m U) 0 HT- 0 Cl) 0 (1) 0 0 Le) Cj) -0. 0 CL C: 0 10 LA 0 0 0 U) U) (1) 0- 0 0 0 z INDEX OF ABUN (A ro CD 3 3 WINTER 3 SUMMER vg;;oO' iw, 7, , m :E CIL 176 stations, abundance was much higher in summer than in winter; however, this was not true at middle shelf stations. Most specimens of M. hispidus were taken at night. In addition to the dominant species discussed above, the index of relative abundance was calculated for other species which were not numerically dominant, but were commercially or recreationally important and of interest in terms of impact or enhancement by oil development. These included the red snapper, Lutjanus campechanus; the gag, Mycteroperca microlepis; and the red porgy, Pagrus pagrus. Red snapper and gag were taken primarily at middle shelf stations (Figures 6.11 and 6.12). These were infrequently caught by the trawl. Com- pared to diver observations and television transects, the 40/54 fly net grossly underestimated the abundance of all large snappers and groupers. Sample sizes were too small to determine seasonal or geographical patterns of abundance for these two species. Red porgy were common at middle and outer shelf stations (Figure 6.13). In winter, P. pagrus was the most abundant species at OS01 and was a dominant species at MS02. In summer, red porgy were dominant only at OSO1. None were caught at inner shelf stations. Most red porgy were taken during the day. Other non-dominant species demonstrated seasonal or diel abundance patterns. All Apogon pseudomaculatus (312 individuals) were captured at all stations, except IS03, in night trawls and only during the summer. All Ophidion spp. were captured at night. Most Centropristis ocyurus (96.5%), Syacium papillosum (96.9%), and Scorpaena spp.(98.2%) were captured at night, whereas most Holacanthus bermudensis (74.2%) and Mullus auratus (95.7%), were trawled during the day. Most Lagodon rhomboides @_88.4%) were captured during winter, and 85.4% of these were taken at night. At inner shelf stations, overall fish abundance was highest in summer when inshore waters warmed up (> 220C). Increased abundance in slimmer was particularly pronounced at IS01 and IS02 (Figure 6.14 and Tables 6.5 and 6.6). Station IS03 had a smaller seasonal difference in fish abundance, and differences in temperature were not as great (Chapter 3). Little seasonal difference in the index of relative abundance was evident for demersal teleosts .at MS02 and MS03; however, seasonal differences present at MS01 were similar in magnitude to the two northernmost inner shelf stations. Station MS01 had the greatest seasonal temperature difference of any middle shelf station. Lowest overall fish abundance was at OSO1. Biomass - Biomass estimates are presented in Table 6.7 for demersal teleost fishes and Table 6.8 for total nekton, i.e. pelagic and demersal fishes, including elasmobranchs, and squid. Mean biomass per tow for all stations was 44.052 kg (demersal teleosts) and 60.011 kg (total) in winter and 30.974 kg (demersal teleosts) and 46.580 kg (total) in summer. In winter, transformed mean catch per tow values were significantly different between stations for demersal teleosts alone (P < 0.005 ANOVA) and for total nekton (P < 0.05 ANOVA). In summer, however, there was no significant difference between stations for either demersal teleost biomass (P > 0.50 ANOVA) or total nekton biomass (P > 0.50 ANOVA). For both seasons combined, @iomass in kg ha-1 was highest at middle shelf depths and lowest at the outer shelf station. Diversity - Diversity varied latitudinally, bathymetrically, seasonally, 177 340 800 South Carolina compechanys ,,34- 2 U. U 0 0 z x 01.0 Wz 0.0 number of ....CHARLE N:-.. %: n occurrences STO N number of samples 0 0 '*ISOI S VANN JOUL *MS01 820 MS02 *0SOI Georgia .2 0 90SO2 IS02 BRUNSWICK MS03 OS03 IS03 JACKSONVILLE 800 Figure 15.11. Relative abundance of Lutjanus campechanus during winter and summer, 1980. 178 340 800 South Corrollinnoo Mycteroperca MICroleps W W2 U. 0 z x a z W ....... 0.0- npumber of n occurrences .-CHA,RLESTONQ number of somp(es R .2 6 16 OISOI A 32*--- 0 S ANNA 10 -L r6 4@ MSOI A. OSOI 820 MS02 Georgia 32* a .2. 6 16 OS02 OIS02 B UNSWICK 0 MS03 0 -5 OS03 IS03 JAC\KSONVILLE.:... 800 Figure 6.12. Relative abundance of r4ycteroperca microlepis during winter and summer, 1980. mom m MMI m M m M M m m u:) rD CD-- ro oc) < IMP (D c: z 0) 01, (D --- Cr Z CL z -3: r) (D 0 r1c) M 10 .10 (n 0 (n ; 0 (J) 0 N 0 10 L.Li 4- 0 0 0 7i (J) INDEX OF 0 0 0 zz ABUNDANCE 0 @ f. 0 b cc nC3 WINTER 33 - (D :147 1 a SUMMER Mi 57- tul @Mll T cid CL CA (D 180 34* Boo South C a rr oo 11 nn a DEMFRSAL FISH ABUNDANCE 8.0- 7.0- Z 6.0- z 5.0- 4.0- L6 - 0 3.0- x ff 2.0- z 1.0- 0.03C ISM [so I k.. "S VANN 0 MS01 *MSO?- OOSOI Georgia 320 OS02 7. IS02 :7 B UNSWICK. MS03 *OS05 IS03 JACKSONVILLE 800 Figure 6.14. Relative abundance of demersal teleosts collected during winter and summer, 1980. 181 Table 6.5. Abundance estimates for trawl-caught demersal teleosts during winter and summer, 1980. Estimated Number of Mean catch per tow Mean catch per tow (retransformed) individuals ha unt.ransformed transformed mean catch per tow of swept area Station Winter Summer Winter Summer Winter Summer Winter Summer IS01 132.0 688.5 3.7 6.0 673.1 913.4 174.8 1000.7 IS02 63.3 848.7 3.7 5.9 79.6 1872.5 81.3 1132.2 IS03 587.8 594.0 5.4 6.1 1252.5 675.3 858.2 926.9 MS01 363.3 513.0 4.0 5.8 1105.1 1069.8 472.4 657.3 HS02 1780.5 1623.7 7.1 6.7 1775.0 1946.1 2031.1 2358.2 MS03 967.7 271.7 6.0 5.2 1559.6 332.9 1253.4 435.0 OS01 33*7 87*5 3,1 4.0 45.2 108.7 48.6 141.6 182 Table 6.6. Abundance estimates for trawl-caught nekton (pelagic and demersal fishes and squids) during winter and summer, 1980. Estimated Number of I Mean catch per tow Mean catch per tow (retransformed) individuals ha untransformed transformed mean catch per tow of swept area station Winter Summer Winter Summer Winter Summer Winter Summer IS01 262.2 740.5 5.5 6.2 264.1 837.4 374.1 1076.3 IS02 81.2 884.2 4.1 6.1 88.3 1394.3 104.2 1179.6 IS03 739.0 925.4 6.3 6.4 852.8 1134.1 1078.9 1444.0 MS01 425.5 645.2 5.2 6.0 645.7 1388.8 553.2 826.6 MS02 1808.2 2087.3 7.1 6.9 1811.1 2718.8 2062.7 3031.6 MS03 1015.7 311.2 6.1 5.5 1613.8 361.1 1315.6 498.2 Osol 849.7 87.8 5.2 4.0 754.7 109.3 1226.0 142.1 183 Table 6.7. Biomass estimates for trawl-caught demersal teleosts during winter and summer, 1980. Mean catch Mean catch Estimated Biomass (kg) per tow (kg) per tow (retransformed) (kg ha-1 of unt mean catch (kg) per tow .kansformed transformed swept area) Station Winter Summer Winter Su=er Winter Summer Winter Summer Isol 2.483 39.559 1.062 3.202 2.782 48.653 3.288 54.497 IS02 6.957 28.984 1.818 2.767 7.390 45.754 8.929 38.667 IS03 44.382 31.433 3.206 3.133 69.085 40.994 65.283 49.049 MS01 26.108 32.101 2.030 3.076 65.489 50.754 33.949 41.129 MS02 147.269 47.822 4.708 3.550 149.693 53.437 168.000 69.456 MS03 70.196 21.922 3.572 2.929 89.044 23.925 90.926 35.100 Osol 10.972 15.076 2.013 2.474 14.232 18.738 15.831 24.397 184 Table 6.8. Biomass estimates for trawl-caught nekton (pelagic and demersal fishes and squids) during winter and summer, 1980. 11--an catch Mean catch Estimated Biomass (kg) per tow (kg) per tow (retransformed) (kg ha-l Of untransformed transformed mean catch (kg) per tow swept area) Station Winter Summer Winter Summer Winter S-mer Winter Summer IS01 8.519 40.122 1.963 3.251 8.886 47.958 11.279 58.316 IS02 7.181 59.441 1.856 3.090 7.629 93.380 9.216 79.300 IS03 .68.529 80.289 4.054 3.549 76.718 114.478 100.050 125.288 MS01 28.893 33.767 2.444 3.125 53.570 54.257 37.566 43.264 MS02 161.724 49.209 4.788 3.590 165.672 54-662 184.489 71.471 MS03 81.304 52.432 3.663 3.280 98.455 56.399 105.314 83.953 OSOI 63.926 16.416 3.214 2.516 59.878 20.603 92.240 26.566 185 and with. light phase (Figure 6.15 and 6.16). The most apparent pattern was the increased diversity of collections made at night (Figure 6.15). At every station, night trawls had higher H' diversity values than day trawls. (See Appendices 15 and 16 for diversity values for individual trawl collections.) Between seasons,-diversity was higher at inner shelf stations during winter (Figure 6.16). Since species richness varied little seasonally at ISOI and IS03 (Figure 6.17)-, increased diversity at these stations in winter is due to the lack.of dominance of the community by a few species (Figure 6.18). Species richness at IS02 was actually much greater in summer, but the dominance of the community by S. aculeatus and H. aurolineatum (Table 6.3) resulted in a lower H' diversity. Diversity at middle shelf stations was equal to or lower than inner shelf stations. Diversity at MS02 was especially low, in spite of high species richness. Large numbers of S. aculeatus dominated at that station (Figure 6.19) during both winter (Table 6.2) and summer (Table 6.3). Unlike inner shelf stations, diversity at middle shelf stations was higher during summer when the two most abundant species were not as dominant (Figure 6.19), and species richness increased (Figure 6.17). Station OS01 had the highest diversit- of any station during both seasons. Although species richness was comparable to other stations with low H' diversity (e.g. MS02), very abundant dominant species were absent from OSO1. Dominance diversity curves for inner shelf stations indicated dominance of the community by one or two species and the increased value of the dominance index in summer (Figure 6.18). Middle shelf stations in summer demonstrated a lower abundance of the most abundant species and/or the increased abundances of other species (Figure 6.19). These trends were associated with a decreased dominance index and a concomitant increased H' diversity. Diversity was higher at OSOI in summer, even though the dominance index (Figure 6.19) indicated increased community dominance in summer. Abundances of all species were low at OSO1, however, and dominance index values were also low relative to other stations. In general, dominance diversity curves indicated that inner and middle shelf live bottom fish communities were dominated by a few abundant species. Several species of intermediate abundance were also present. An obvious feature was the large number of rare species, many of which were represented by a single specimen. Cluster analysis - Normal cluster analysis demonstrated the importance of light phase in determining the community composition of trawl collections (Figures 6.20 and 6.21). The broad grouping of collections by light phase resulted in no clear grouping of collections with respect to depth or lati- tudinal zones, and most groups contained collections from more than one station, especially in winter. Grouping of stations by light phase was more pronounced in summer. At that time, collections were grouped primarily by time period (day versus night), but were also more clearly grouped by depth zone within each light phase. Because normal cluster analysis resulted in grouping of collections from different stations, and because of the interest in describing faunal affini- ties of species groups with regard to our selected study areas, site groups as defined by normal analysis were not used in normal-inverse comparisons by nodal analysis. Instead, species groups as defined by inverse analysis were compared to each station. Fidelity and constancy comparisons were made between species groups and each station; and between species groups and day 186 34* 800 South Carolina DEMERSAL FISH DIVERSITY Uj H All. --CHARLESTON.'.. isol S VANN 82* *OS01 MS02 Georgia 320 OS02 3:SO2 8 UNSWIC MS03 OS03 IS03 JACKSONVILLE-_ 900 Figure 6.15. Shannon diversity (11') for pooled replicate samples,of demersal fishes at each station, by light phase and season. 187 34" 800 .... .. South Carolina DEMERSAL -:,.FISH DIVERSITY ww. o-1340 Lj H4 3, -iM Mi -'c ON- .:,:.,H:ARLEST Ism Cz 32--l 'S VANN H M 01 90sol MS02 Georgia 320 9OS02 *ISOP_ BRUNSWICK MS05 *OS03 *IS03 JACKSONVILLE-'.. 800 A. Figure 6.16. Shannon diversity for pooled replicate samples of demersal fishes at each station durina winter and summer, 1980. 188 340 800 South Carolina DEMERSAL ..FISH DIVERSITY 4- UJ Uj SR - I.- I Z2 Jill -CHARLESTON- ... eisol SAVANNAH MS01 820 MS02 0sol Georgia 320 OIS02 osop- BRUN ICK. OMS03 OS05 IS03 JACKSONVILLE.- 800 Figure 6.17. Species richness (SR) for pooled replicate samples of demersal fishes at each station during winter and summer, 1980. 189 STATIONS 10,000T 1SO1 ISO2 IS03 WINTER D.I.-62.4% WINTER D.I.=66.3% WINTER D.I.z69-6% o SUMMER D.1.z6I.T% o SUMMER D.I.-84.6% o SUMMER D.l.s89.2% D 0 1000- U) -j 0 > 0 .0 0 0 100- LL 0 0 0 0 0 GD w 0 0 0 0 0 % OD 00 z 0 0 co 10- 0 0 0 0 0 o 0 0. 0 -Ir . am 16 , go 10' iO 50 16 io SPECIES SEQUENCE Figure 6.18. Dominance diversity curves and dominance index (D.I.) values for demersal fishes collected at inner shelf stations during 1980 sampling. 190 STATIONS MSO( MS02 MS03 OSO, WINTER 0.1Z.-92.6 WINTER 0.1. - 95.2% WINTER D.I.- 78.6% -WINTER O.J.-45.9% SUMMER 0.1.0Z8%; -SUMMER O.L-93.0%1, SUMMER 11,1,17-.0-16 ISUM-ERO@'_-5-5% 1000__@ 100- 0 w 10 3'0 iO 10 30 50 10 30 50 10 36 50 SPECIES SEQUENCE Figure 6.19. Dominance diversity curves and dominance index (D.I.) values for demersal fishes collected at middle and outer shelf stations during 1980 sampling. 191 Dernersal Fish: Station Groups SIMILARITY 1.0 .6 -.,2 -.16 1 -1.0 Group Station Period IS03 N IS03 N IS03 N IS02 N 'TAW3 - 9- MS03 N MS03 N MS03 D MS03 D MSO I N MSM - 9- MS02 N MS02 N MS02 D MSO I D IS03 D MS02 D MS02 D -Osol N- 4 OSO1 N I N _gSQ. isol IS01 N 5 isol N IS02 N IS02 N OSO1 D 6 OSO1 D OSO1 D M @ -01- a- - - - MS01 N 7 IS01 D MS01 D IS02 D - -TSO-2 - 6- IS02 D isol D 8 IS03 0 IS03 D MS03 D IS01 D 1.0 .6 .2 -.2 6 -1.0 SIMILARITY Figure 6.20. Normal cluster dendrogram of winter trawl collections of demersal, fishes. D = day trawls and N = night trawls. 192 Dernersal Fish: Station Groups SIMILARITY 1.0 .6 .2 -.2 -.6 -1.0 Group Station Period IS02 N IS02 N IS02 N isol N isol N isol N IS03 N IS03 N msul- -4- MS03 N MS01 N MS01 N 2 MS02 N MS02 N MS02 N MS01 N MS03 N - msuz- - b- MS02 D MS02 D 3 MSO I D MS03 D MS03 D MS01 D ts6l IS03 D IS02 D IS03 D 4 IS03 D IS01 D IS01 D IS01 D MS03 D 102- CF- 5 mso i D OSO1 D b0l OSO1 N 6 OSO1 N OSO1 D OSO1 D 1.0 .6 .2 -.2 -.6 -1.0 SIMILARITY Figure 6.21. Normal cluster dendrogram of summer trawl collections of demersal fishes. D = day trawls and N = hlight trawls. 193 and night collections at each station, because normal analysis indicated distinct. differences in day and night trawl collections. Winter inverse and nodal analysis indicated that several species fre- quently co-occurred within a particular depth zone or during a particular light phase. Sp6cies groups B, H, and I (Figure 6.22) were more faithful to inner shelf stations (Figure 6.23). These species were rare and common live bottom (C. ocell*tus, A. probatocephalus, C. striata, E. umbrosus), coastal, or open shelf species (Prionotus spp., Urophycis sp., 2. chrysopter:D which fre- quently occur inshore [habitat information from Struhsaker (1969)]. Several species groups (Groups C-E) demonstrated moderate to high constancy and fidelity to middle shelf stations in winter. These groups comprised common to abundant live bottom species (E. lanceolatus, H. aurolineatum, S. aculeatus), including priority species of commercial importance (L. campechanus, P. pagrus, R. aurorubens). Other species which were ubiquit-ous -across the shelf (Groups G and J) were more frequent (higher in constancy) at middle shelf stations. Only species Group F demonstrated much faithfulness to OS01 in winter. It was composed of deep-living sand bottom species. Several species were more frequent in night trawls (Groups A, G, H) in winter (Figure 6.24). These groups consisted of both live bottom and open shelf species. In summer, some species groups (Groups A-C) were high in constancy at inner shelf stations, while several groups (Groups G-J) rarely occurred at those depths (Figures 6.25 and 6.26). Three groups (Groups E-G) demonstrated more than low fidelity to inner shelf stations, and, as in winter, these groups consisted of inshore live bottom and open shelf species. Two species groups were faithful to middle shelf depths (Groups H and J) in summer. These groups included two priority species, L. campechanus and M._ microlepis. As in winter, several species (Group C), including the priority species R. aurorubens, that were ubiquitous across the shelf were more frequent at @17@d_fle shelf depths. Species Group D was highly faithful to OS01 in summer. This group included species which were taken only at OS01 [Equetus (= Pareques) sp. nov., C. sedentarius] or which were more abundant at that station (P. pagrus, Echiodon sp. nov., P. salmonicolor). Pagrus pagrus, a priority species, was more frequent at OS01 in summer but more frequent on the middle shelf in winter. Several species forming Groups A, B, F, and G were more frequently caught in night trawls in summer (Figure 6.27). These groups included species which were also more frequent in night trawls in winter (e.g. 1. holbrooki, Scorpaena spp.), as well as species which were only abundant during slimmer and were-more abundant at night (e.g. A. pseudomaculatus, P. plectrodon). Several species co-occurred in th@_esame depth zone in both winter and summer, whereas other species apparently moved inshore or offshore. Thus, L. rhomboides and 0. chrysoptera co-occurred in the same species group which was faithful to inner shelf stations in both winter and summer. The priority species L. campechanus co-occurred in the same group with H. bermudensis in both winter and summer, and these species were most frequent at middle shelf stations during both seasons. Many species were ubiquitous across the shelf (e.g. R. aurorubens, H. aurolineatum) but were more abundant on the middle 194 SIMILARITY 1-0 .6 .2 -.2 -.6 -1.0 Group Species Prionotus ophryas Ophidion beani Urophycis earl1i A Scorpaena brasiliensis Scorpaena calcarata Mustelus canis Prionotus scitulus Chaetodon ocellatus B Dasyatis americana Chilomycterus schoepfi Archosargus probatocephalus Parablennius marmoreus Dasyatis sayi Trachinocephalus myops Lutjanus campechanus D Sphoeroides spengleri Equetus lanceolatus Holacanthus berrudensis Diplodus holbrooki Pagrus pagrus E Priacanthus arenatus Aluterus schoepfi Chaetodipterus faber - - - - aaEdus -poeyl- - - F Dasyatis centroura - G-oph7c-is -regiia- - - Syacium papillosum G Ophidion holbrooki Centropristil ocyurus Prionotus sp. H Urophycis sp. Prionotus carolinus Orthopristis chrysoptera Lagodon rhomboides Centropristis striata Equetus umbrosus Monacanthus hispidus Lactophrys quadricornis Diplectrum formosum Calamus leucosteus Synodus foetens Rhomboplites auror7bens- Haemulon aurolin-e-atum Stenotomus aculeatus 1-0 .6 .2 -.2 -.6 -1.0 SIMILARITY Figure 6.22. Inverse cluster dendrogram of winter trawl collections of demersal fishes. S17 STATIONS Tqnl Tqn9 Tq03 M-,n1 KA Qn ';0 KAQn-A Acni A 0- B CONSTANCY C 0 > 07 Very @i'h D 9 E [email protected] High F ........... W 0.?@OZModerote G E][email protected] Low H 0- E] < 0. 1 Very Low K -.6 -.2 .2 SIMILARITY Cn ISOI IS02 IS03 MSOI MS02 MS03 OSOI A B a_ FIDELITY 7) C 0 D 02@ 4 Very High ........ .... .. ..... .. X.. (D E 0>3High ............ ...... F Q12 Moderate LLJ G W H Low a- El < I Very Low W K .6 --%2 .2 SIMILARITY Figure 6.23. Inverse classification hierarchies and nodal diagram showing constancy and fidelity of station species group coincidence based on winter collections of demersal fishes. 196 STATIONS 0 0 0 000000 H H H H H H 2 2 a 2 2 2 0 D N 0 N_ D N 0 N D N D N D N A D C CONSTANCY 0 E20.7Very High Ir D CD E jaza5 High U) F @Z0.1iModerole W G H 020 1 Low W 0. <0.1 Very Low U) 0 Z'K -6 12 SIMILARITY o o c> 0 0 0 0 0 0 0 U) 0 U) H H H H H H 0 0 D N D N 0 N D N D N D N D N A IL F DELITY c 0 B24 Very High x D U) E . . . . . . . . . . 1113High . . . . . . . . . . F 922MOdelOte G H 1321 Low W CL 0 < I Very Low Lq K r_1__r__T__1 -S -2 SIMILARITY Figure 6.24. Inverse classification hierarchies and nodal diagram showina con- stancy and fidelity of station - snecies group coincidence 6ased on winter collection of demersal fishes. Stations are separated into day and night collections. -EZ 1_q 197 SIMILARITY 1.0 .6 .2 -.6 -1.0 Group Species I Ophidion holbrooki Centropristis ocyurus pseudomaculatus Equetus uffbrosus Porichthys plectrodon Scorpaena brasiliensis Syaciun papillosum Scorpaena calcarata -T q LTa-d r i @-or n i Synodus foetens Centropristis striata B Monacanthus hTSPIdus Prionotus carolinus Diplectrum fo"nosum Hie-muI67auFo-iin-eawn- Stenotomus aculeatus C Calamus leucosteus Rhomboplites aurorubens Pagrus pagrus Equetus (= Pareques) sp. nov. Serranus phoebe D Echiodon sp. nov. Chaetodon sedentarius Ophidion beani Prionotus salmonicolor rui-voli'lans - E Balistes capriscus Prionotus scitulus Orth(@p-risi-is Ch-rys t-era- - Chaetodipter S fTb-er Lagodon rhomboides F Chilomycterus schoepfi Prionotus ophryas Sphoeroides maculatus Ariosoma Oalae7cum- - - Gymnothorax saxicola G Prionotus roseus Paralichthys albigutta UroEhycis earl1i Aluterus schoepfi Holacanthus bennudensis H Lutjanus campechanus Mycteroperca micrOlePiS Priacanthus arenatus Synodus k2tL Equetus lanceolatus Halichoeres bivittatus Diplodus holbrooki Archosargus probatocephalus Chaetodon ocellatus Parablennius marmoreus Trachinocephalus myops Bothus sp. Synodus interffedius 1.0 .6 .2 -.2 -.6 -1.0 SIMILARITY Figure 15.25. Inverse cluster dendrogram of summer trawl collections of demersal fishes. STATIONS ISOI IS02 IS03 MSOI MS02 MS03 OSOI A CL B . . . . . . . . . . CONSTANCY D c 0 ... NIO.T very High W D EM10.5 High CD E (n F [email protected] W G im: I" [email protected] W H CL 0 < 0.1 Very Low Cn -1.0 @6 @2 SIMILARITY ISOI IS02 IS03 MSOI MS02 MS03 OSOI A 00 0. FIDELITY D c LMER. 0 N 2.4 Very High M32@!IHigh E Issm, I F E] k2 Moderate W G E021 Low U W H E] < I Very Low 0- -1.0 -"6 @2 '2 SIMILARITY Figure 6.26. Inverse classification hierarchies and nodal diagram showing constancy and fidelity of station species group coincidence based on summer collections of demersal fishes. STATIONS Cy ej ro to - E; C'J 10 10 0 0 0 00 0 0 0 0 3 _0 2 En u) cn w cn Zn in w m k H 2 X. 1 2 2 2 0 0 D N _D_ N D N D N D N D N D N A 0- D 0 c CONSTANCY > 0.7 Very High D cn E !9M 010.5 High Q103MOderate W F E310.1 Low W G CL H E] < 0.1 Very Low U) ........... JL `-M __J -1.0 6 2 .2 Cy Cy in in - - C%J N rn in - - SIMILARITY 0- 0 0 0 0 0 0 0 0 0 0 0 (n 0 (n tn (n (n 0 0 0 0 0 %.D H H H H 2 2 2 2 2 0 0 D N D N_ D N D N D N D N D N A CL D fIDELITY 0 W 14 Very High D High E M3 Q2@2 Moderate W 7-=F G I Low E] 0 Very Low CL H L 11 -1D -6 -.2 .2 SIMILARITY Figure 6.27. Inverse classification hierarchies and nodal diagram showing constancy and fidelity of station - species group coincidence based on summer collections of demersal fishes. -Stations are separated into day and night collections. 200 shelf and demonstrated higher constancy at middle shelf stations during both seasons. The associations and fidelity patterns of some species varied seasonally, perhaps due to migratory movement. Pagrus pagrus, for example, was most faithful to MS02 in winter but was included in a group which was highly faithful to OS01 in summer. Fishes Observed or Collected by Other Gear: I I Underwater Television - Approximately 40 species of fish could be identi- fied on the videotapes (Tables 6.9 and 6.10). With the exception of Sphyraena barracuda and Mycteroperca phenax, which were frequently observed by divers, all species were caught by @_ther @emoval gears, and most were taken by trawl. Underwater television estimates of abundance were generally higher than trawl estimates (Table 6.11). Videotape analysis showed differences in fish abundance among the three depth zones. Tomtate (Haemulon aurolineatum) was the most abundant species seen and was most abundant at middle shelf stations, especially MS01. Black sea bass (Centropristis striata) were also commonly observed in all three depth zones and were most abundant on the middle shelf. Red snapper (Lutjanus campechanus) were occasionally seen in all three depth zones, and gag (.Mycteroperca microlepis), red porgy (.Pagrus pagrus , and greater amberjack (Seriola dumerili) were commonly observed at middle and outer shelf stations. Underwater television was particularly useful for assessing species composition and abundance at those outer shelf stations which could not be trawled. Based on videotapes, the outer shelf is dominated by yellowtail reeffish (Chromis enchrysurus , red porgy Q. pagrus , blackbar drum [Equetus (= Parequis sp. nov.], gag (Mycteroperca microlepis , and other large groupers (.Mycteroperca spp., Serranidae). With the exception of MS03, OS01, and OS03, fish density (numbers of individuals per hectare of transect) was lower at all stations in winter. In winter, few fish were recorded on videotape at inner shelf stations, particu- larly IS01. Density varied widely from station to station at middle shelf depths and was lowest at MS02 and highest at MS03. Stations OS01 and OS02 had similar fish densities, but OS03, a very high relief station, had higher fish densities which were comparable to MS01. In summer, underwater television transects indicated higher fish density, as compared to winter observations, at all inner shelf stations. Density again varied widely from station to station on the middle shelf and, in contrast to winter television transects, was highest at MS01 and lowest at MS03. Density of fishes at OS01 was similar to winter observations, but many more fish were observed in summer than in winter at OS02, whereas fewer fish were seen at OS03 in summer. Diver Photographs and Swimming Transects - Results from analysis of the hand held camera photographs were of limited value due to poor visibility in many photographs and limited bottom time on some dives, but the photographs do provide some useful comparison data. Photographic fish counts indicated increased fish abundance in summer (Table 6.12) as was noted also in trawl collections and television transects at comparable stations, particularly IS01. No Centropristis striata were Table 6.9. Abundance of fishes counted at each station on videotape transects during winter, 1980. Species Station IS01 IS02 IS03 HS01 MS02 MS03 OS01 OS02 OS03 Atuterus app. 1 3 Anguilliformes - - - Lrehosargus probatocephalus 1 36 2 Balistes capriscus - - - - 1 1 2 Ballatidae - - 2 - Calamus leucosteus? - - - 2 Centropristis ocyurus - - I - 1 9 Centropristis ocyurus? - - - 3 2 Centroprtstio app. - - - 3 Centropristis op.? - - - - - 3 Centropristis striata 22 32 - 99 1 8 5 8 - Chaetodon app. - - - - - - 7 Chromia enchryourus - 2 - - 3 125 Dasyatls sabina - - - - t Dasyatls sp. - - - - - I I Decapterus punctatuB? - 9 - - - 33 Diplectr formosum - - - - 5 - - Diplectr formosum? - - - I I - - I C) Diplodus holbrooki - - - 3 1 - 2 Equetus lanceolatus - - - - 2 - - Equetus app. - - - - - - 29 - tquetus Pareque ) sp. nov. - - - - - - 1 2 4 jq!jetus Pareques) op. nov.? - - - - - - 3 - - Equetus umbrosus - - - 61 - - - - Fistularia tabacaris - - - - - - - 2 Haemulon aurollneatum - - - 800 - - - - Haemulon plumiert - I - - - Holacanthus berm@densls - 5 - 5 - 2 8 1,@ctophrys !I@jadrlcornis - - - Lutjanus campechanus - - Lutjanus campechanus? - - I Huraenidae - - Mycteroperca microlepto - - - 12 7 4 Hycteroperca microlepts? - - - - - Mycteroperc op.? - - - - - I Pagrus pagrus - - - 24 3 3 3 46 Pagrus pagrus? - - - - I - 2 Priacanthus app. - - - 9 1 Prionotus op. - - - I Rhomboplites aurorubens - - - - - - I Rhomboplite aurorubens? - - - - 2000 4 36 675 �Lorp_@epa app. - - I - - Serlola dumerill - - - 5 1 - 2 3 Serraoidae (Grouper) - - 10 - - 1 2 25 Table 6.9 (Continued) Species Station ISOI IS07 IS03 MS01 NS02 MS03 OSOI OS02 OS03 Serranidae? - - 2 Sparidae - - - 2 5 Stenotomus aculeatus - - 14 4 Stenotomus aculeatus? - - 15 - - - - - - Unknown demersal 12 20 40 42 61 42 107 497 2874 Total 35 89 82 1067 97 2061 175 624 3779 Total number of transects: 3 4 3 6 4 3 4 6 6 Total hre. of analyzed videotape: 0.97 0.81 o.95 0.74 0.63 0.70 0.76 1.24 1.91 Total length of transects (m): 3012 2637 '2833 1733 2070 2157 1838 5244 5991 Number of fish per transect 11.7 22.3 27.3 177.8 24.2 687.0 43.8 104.0 629.8 Number of fish per hr of videotape 36.1 110.1 86.1 1444.1 153.2 2956.0 230.5 503.7 1983.1 Number of fish per too m of transect 1.2 3.4 2.9 61.6 4.7 95.6 9.5 11.9 63.1 Number of fish per ha of transect 34.2 99.3 85.1 1810.9 137.8 2810.3 280.0 350.0 1855.2 CD I,Q Table 6.10. Abundance of fishes counted at each station on videotape transects during summer, 1980. Species -tatlon IS01 IS02 IS03 MSOI MS02 MS03 OSOI OS02 OS03 Anguilliformes I - 2 Archosarguo.probatocephalus - 4 7 Bothidae - - Calamus leucosteus - - c@la u leucosteus? 2 - 4 Carangidae 2 - Carcharhinus sp. - - Centrojr-istis ocyurus - - - - - - 1 6 Centropristis striata 8 7 18 75 27 16 1 10 2 Chaetodipteru faber - 28 - - - - - Chaetodon ocellatus Chaetodon sedentarius Chaetodon spp. 4 - 2 3 21 5 Chromis ench!y uru@ 10 2 - 23 103 57 pasya@ls centroura @asyatts op. Echeneidae Equetus lanceolatus Equetus (- Pareque op. nov. - - 4 2 Uj Equetus umbrosus - 25 - - g.ym!!othorax sp. - - 1 8 18 1 Haemulon aurolineatum - 139 36 8295 4177 Halichoeres sp. - - I Holacanthus bermudensts 12 4 1 1 2 7 Lut]Atj@s campechanus - 2 1 1 Lutjanus campe hanus? - Muraenidae - 8 2. 6 3 _y_Steroperca microlep!s - 16 - 2 - Myvterpp_@rca q!Lc@rolepls? - - - !ijcteroperca sp. - - Pagrus pagrus - - 1 4 2 Priacanthidae - - 3 - - 10 1 Prlacanthidae? - - Prionotus spp. 2 - Prionotus op.? - - Scomberomorus app. 2 - 2 3 Serlola dumerill - - 40 185 Serranidae (Grouper) - - - - 52 Serranus Rh4webe - - @p@iqtroides opengleri? - - �&yraLena barracuda - 34 @phy!1a,qa !IarracuLa? - - Stenotomus aculeartuS 64 15 5 78 1 Table 6.10 (Continued) Species Station IS01 IS02 IS03 HS01 MS02 MS03 OSOI OS02 OS03_ Stenotomus aculeatus? - 2 - - Synodus spp. 1 - I - 1 4 - - - Unknown demereal 2050 387 454 3793 176 228 132 1537 232 Total 2133 599 536 12259 4696 270 169 1777 323 Total number of transects: 3 3 3 3 3 4 3 6 6 Total hrs. of analyzed videotape: 0.89 0.97 0.99 1.02 1.01 1.02 1.01 1.92 2.00 Total length of transects (m): 2978 2400 2533 2164 2278 2472 2032 5580 5112 Number of fish per transect: 683.3 199.7 178.7 4086.3 1565.3 67.5 56.3 296.2 53.8 Number of fish per hr of videotape: 2299.1 619.7 537.5 11960.0 4670.0 263.4 166.7 923.1 161.3 Number of fish per 100 m of transect: 68.8 25.0 21.2 566.6 206.1 10.9 8.3 31.8 6.3 Number of fish per ha of transect: 2106.6 734.1 622.4 16661.7 6063.1 321.2 244.6 936.6 185.8 PJ C) Table 6.11. Abundance estimates (number of individuals. ha-1) of selected species, based on television and trawl analysis. Inner Shelf Middle Shelf Outer Shelf Winter Summer Winter Summer Winter Summer Species TV Trawl TV Trawl TV Trawl TV Trawl TV Trawl TV Trawl L.. Archosargus probatocephalus 13.52 0.98 4.09 0.85 0.00 0.90 0.00 0.16 1.60 0.00 0.00 0.00 Centropristis striata 18.72 5.48 12.27 35.08 53.30 3.24 50.20 3.74 20.80 0.00 18.82 0.00 Holacanthus bermudensis 0.00 0.00 0.00 0.00 4.93 0.76 7.23 1.51 16.00 0.00 14.47 0.27 Lutlanus campechanus 0.35 0.00 0.00 0.17 0.00 1.65 0.85 0.48 0.00 0.00 2.89 0.27 Mycteroperca microlepis 0.00 0.00 0.00 0.00 5.92 0.07 10.21 0.24 17.60 0.24 15.92 0.00 Seriola dumerili 0.00 0.00 0.00 0.17 2.96 0.00 96.56 0.08 8.00 0.48 5.79 0.27 C tP 206 Table 6.12. Abundance of fishes seen in photographs taken by divers using the still camera during winter and summer, 1980. ISM IS02 IS03 MS01 M502 MS03 Species w s w S w s V 8 w 3 w s Archosargus probatocephalus 16 1 2 Centropristis spp. 2 Centropristis striate 109 79 4 1 20 13 Decapterus punctatus 22 Engraulidae 1105 Haemulon aurolineatum 34 210 Haemulon plumieri 1 2 Halichoeres app. 16 Holacanthus bermudensis 2 1 13 Lutjanus campechanus 7 Mvcteroperca microlepis 1 5 8 Mycteroperca phenax 20 Mycteropercs spp. 1 12 1 7 Pagrus palrus 3 15 31 Pomacentrus laucostictus 27 Seriola dumerili 1 Sparidae 4 19 8 1 Stenotomus spp. 20 Unidentified 14 27 30 2 34 2 7 Total 0 203 141 - - 250 4 46 37 54 1225 Number of stops 9 9 8 - - 7 3 3 8 7 9 Number of fish per stops 0.0 22.6 17.6 - - 35.7 1.3 15.3 4.6 7.7 136.1 photographs unreadable no photographs taken 207 photographed and few were captured by trawl at IS01 in winter. In slimmer, however, C. striata was abundant in diver photographs and in trawl collections. Archosargus probatocephalus were commonly seen in photographs at IS02 in winter and were also commonly seen in videotapes at that time, but few were captured by trawl. Also noteworthy was the abundance of groupers (Myctero- perca slip.). Few of these large groupers were captured by any fishing gear, but they were commonly seen in photographs and on videotapes, especially at middle shelf stations. Because transect length and visibility varied, results of the diver swimming; transects are not quantitative, but are useful for making qualitative comparisons with other gears. The most noticeable differences in the fish community as seen by divers were the number of large predatory fishes observed (Table 6.13). Divers observed more large groupers (Mycteroperca spp.) than were captured or observed on videotapes or photographs. Particularly surprising was the number of M. phenax seen at MS01 and MS03 in summer. This species was not captured by any fishing gear. Lutjanus campechanus was also commonly seen at M103, even though few were captured there by removal gears. Archo- sargus probatocephalus was abundant at ISO2, but few were captured by trawl. Baited Fishing Gear - Fifteen species of fishes were captured on the vertical. longlines. Centropristis striata was the most abundant and frequently collected species (Table 6.14), and@ was-taken at every station except OS01 and OS03. This species dominated collections at the inner shelf stations. Pagrus pagrus, another priority species, was only taken at middle and outer shelf stations, a distribution pattern also noted in trawl catches. One L. campechanus and two R. aurorubens were taken at outer shelf stations. Longline catches were generally low and averaged 1.1 fish per hour of fishing time. Longlines did not catch many large predatory fishes they were deployed. to catch, and all species collected were also captured by trawl. Snapper reels were more selective than longlines, and only eight species of fish were taken with this gear (Table 6.15). Centropristis striata and Pagruspagrus were the most abundant species caught. Centropristis striata was most abundant at inner and middle shelf stations, and P. pagrus and C. yurus were most abundant at middle and outer shelf stations, a pattern reflected in collections by other gears. oc Snapper reels ca'ught more fish per hour of effort than did vertical longlines. Average catch per hour of fishing was 4.2 fish. Snapper reels caught priority species (C. striata, P. pagrus, R. aurorubens) which were also conmonly taken in trawls. They were, however, effective in catching P. pagr s at outer shelf stations which could not be trawled. Snapper reels did not catch any large predatory priority species. Antillean S-traps caught 10 species of fish, three of which were priority species (Table 6.16). As with other baited gear, C. striata.and P. pagrus were the dominant species caught, with C. striata dominating cat at inner and middle shelf stations, and P. pagrus dominating catches at middle and outer shelf stations. Dominant and priority species captured were also taken by trawl; however, the traps caught many specimens of priority species at outer shelf stations which could not be trawled. In addition, one specimen of Corniger spinosus, a rare species not taken by other gears, was captured in an AnCillean S-trap. Antillean S-traps were the most efficient baited gear deployed, with an average catch of 5.5 fish per hour. 208 Table 6.13. Abundance of fishes seen by divers along swimming transects during winter and summer, 1980. Isol IS02 IS03 MS01 MS02 MS03 Species w 9 w a w s w s W a w s Acanthurus chirurgus - - - - - - 1 AdItobatus narinari 1 - - - - - - Aluterus schoepfi - - 3 - - - 12 Aponon pseudomeculatus 15 - 1 - - - - - 15 Archosarsus probatocephalus 3 56 25 - 20 1 6 - - - 8 Balistidae - - - - - - - - 1 12 - - Blenniidae 1 3 - 15 Calamus spp. - 2 5 30 200 10 - - Caranx ruber - - - - - - - 60 Centropristis Philadelphicus - - - - - - Centropristis spp. - 2 - - 12 4 Centropristis striata 2 130 325 100 25 30 12 30 150 86 10 - Chaetodipterus faber - - - 35 - - - 25 - - - - Chaetodon ocellatus - - - - - - - - - 1 - 5 Chaetodon op. - - - - - - - - 1 - - - Chromis op. - - - - - - - Chromis cvaneus - - - - - - I Decapterus spp. - 30 - - - 10 - - - Diplectrum formosum - - - 4 - - - - - Diplodus holbrooki - - 1 2 - - - - - Engraulidae - - - - - - - - 999 Equetus lanceolatus - - 1 - - - - - - Equetus punctatus - - - 4 - 5 - - - Equetus umbrosus - 3 100 - 100 8 50 - 44 Gymnothorax spp. - - - - I - - - - Haemulon aurolineatum - 100 - 150 - 200 - 100 - - Haemulon plumieri - - - - - - - 1 - 3 Halichoeres bivittatus - - - 5 - - - - - - Holacanthus bermudensis - - 1 3 - 10 15 6 1 2 - 24 -9b-ridae - - - 25 - - - - - - - 31 Lutlanus campechanus - - - - - - 1 - 9 1 63 Mycteroperca microlepis - 4 8 - 5 1 6 20 20 - 20 Mycteroperca phenax - -- 2 - - 7 26 - - - 34 Opsanus spp. 2 - - - - Op"nus tau - 2 - 3 30 - - 2 - - Pastrus @&-Arus - - 137 - - 25 20 60 3 52 Pomacentrus leucostictus - 1 - - 1 - 12 - 24 - 75 Pomacentrus variabilis - - - - - - 1 - 1 - - Pristigenys alto - - - - - - - - 1 - - Remora remora - - - - 2 - - - - Rypticus maculatus - - - - 2 - - - - Scomberomorus cavalla - - 2 Seriola dumerili - 20- -6 - 30 !ierranui -subligarius - 1 30 - 5 - - - - - 3 Sphyraena barracuda - - 20 - 1 - 6 - - - - Stenotomus spp. - 100 15 - - - 25 - - - - Synodontidae - - - - - - - - - 1 - Synodus foetens - I - - - - - - - - - UroRhycis spp. - - - - 15 - - - - - - Total 5 372 533 577 25 639 91 160 193 414 27 1470 Transect duration (min) 20 16 18 28 17 20 17 14 20 23 15 16 Number of fish observed per min 0.2 23.3 29.6 20.6 1.5 32.0 5.4 11.4 9.6 18.0 1.8 91.8 MM MM M M M MMM M M MM M M M @' Table 6.14. Abundance of fish species caught on vertical longlines during winter and summer, 1980. n - number of lines which caught fish and N - number of lines deployed. Station ISM IS02 IS03 MS01 MS02 MS03 Osol eS02 OS03 Species w a w a w a w a w a w a w a w a w 0 Calamus leucosteus .!@@ro j@tqtls ocyuru 2 Centropristis striata 6 4 7 3 8 5 3 4 11 7 2 2 Diplectrum formosum I Haemulon aurolineatum I Haemulon plumierl I Lutlanus campechanus Mustelus canto 7 3 1 C:) Ophichthus ocellatus I Opsanus pardus I Pagrus pagrus 5 3 1 1 3 Paralichthys albigutta I Rhizoprionodo terraenovae 2 1 1 Rhomboplites aurorubens Serlola dumerill. 1 n/N 8/8 5/8 4/8 4/8 6/8 4/8 6/8 3/8 6/8 5/8 5/8 2/8 3/8 4/8 1/6 4/8 2/8 0/2 Total number of fish 13 7 8 4 9 5 7 .4 17 9 8 2 4 5 1 9 2 0 Catch per line (n) 1.7 1.4 2.0 1.0 1.5 1.3 1.2 1.3 2.8 1.8 1.6 1.0 1.3 1.3 1 2.2 1 0.0 Total soak time (hro) of n lines 10.6 7.4 5.3 6.1 6.6 4.0 9.7 3.3 8.1 5.9 7.3 2.2 5.7 4.8 1.4 5.0 3.0 0.0 Catch per hr of n lines 1.2 1.0 1.5 0.7 1.4 1.3 0.7 1.2 2.1 1.5 1.1 0.9 0.7 1.0 0.7 1.8 0.7 0.0 Table 6.15. Abundance of fish species caught on snapper reels during winter and summer, 1980. n number of reels which caught fish and N - number of reels fished. Station ISM IS02 IS03 MS01 MS02 MS03 Osol OS02 OS03 Species w 0 w a w a w 0 v a w a w a w a W 8 Centropristis ocyurus 1 3 2 4 2 7 Centrop!Istis striata 8 12 4 1 7 3 2 4 8 9 1 1 Diplectrum formosum I I Haemulon aurolineatum 1 Opsanus pardus 1 Pagrus pagrus 2 3 2 1 2 12 Rhizoprionodon terreenovae I CD Rhomboplites aurorubens I n/N 0/6 516 316 3/6 1/6 5/6 316 3/6 2/6 5/6 6/6 4/6 2/6 2/6 3/6 0/6 4/6 0/3 Total number of fish 0 8 12 4 1 7 4 6 4 10 15 8 2 2 4 0 20 0 Catch per reel (n) 0.0 1.6 4.0 1.3 1.0 1.4 1.3 2.0 2.0 2.0 2.5 2.0 1.0 1.0 1.3 0.0 5.0 0.0 Total soak time (hro) of n reels 0.0 1.4 2.0 0.8 0.2 1.2 2.6 0.8 1.0 1.2 4.0 1.0 1.4 0.6 1.3 0.0 2.6 0.0 Catch per hr of n reels 0.0 5.8 6.0 5.0 4.0 6.1 1.5 8.0 4.0 8.0 3.8 8.0 1.5 3.5 3.2 0.0 7.7 0.0 MM M "M M M MMM MM M@Mm "@' Table 6.16. Abundance of fish species caught In Antillean S-traps during winter and summer. 1980. n - nnmher of trans which raieght flah and N - number of traps deployed and recovered. Station isol IS02 IS03 HS01 NS02 NS03 OSOI OS02 OS03 i.. I Species w a w a w 8 -W ---- a - w a w a w 0 w a w a. Centropristis ocyurus 1 2 20 5 1 9 2 8 17 Centropristis striate 2 22 2 12 4 16 27 1 48 17 2 3 Corniger spinosus 1 Diplectru formosum 1 Epinephelus drummondhayi I Haemulon aurollneatum 3 1 8 2 Opsanus sp. I Pagrus pagrus 1 6 30 6 1 3 is 1 52 10 F, Rhomboplites aurorubens 1 2 Stenotomus aculeatus 1 3 2 n/N 2/4 4/4 0/4 -1/4 3/4 2/4 4/4 3/4 2/4 1/4 4/4 4/4 2/4 1/4 3/4 2/4 3/4 1/1 Total number of fish 2 25 0 2 14 5 19 9 36 1 101 30 2 3 30 a 62 27 Catch per trap (n) 1.0 6.2 0.0 2.0 4.7 2.5 4.8 3.0 18.0 1.0 25.2 7.5 1.0 3.0 10.0 4.0 20.7 27.0 Total soak time (hrs) of n traps 2.1 4.0 0.0 0.8 3.1 1.4 7.0 2.6 4.1 0.8 4.8 3.5 2.5 1.6 5.4 2.0 3.5 5.1 Catch per hrof n traps 1.0 6.2 0.0 2.5 4.5 3.6 2.7 3.4 8.7 1.2 21.2 8.6 0.8 1.9 5.5 3.9 17.6 5.3 212 Rectangular Antillean traps were less efficient than S-traps. Average catch was 3.5 fish per hour (Table 6.17). Centropristis striata was the dominant species collected and was most abundant at inner shelf stations. Other priority species captured were L. campechanus and P. pagrus. These species were also captured by trawl at those stations. Ass4@ssment of Larval and Juvenile Fishes: A total of 8717 larval and juvenile fishes, representing 119 taxa, were collected in 36 epibenthic sled tows. Of the 119 taxa, 43 represented species, 40 represented genera, 34 represented families, and two represented subfamilies. Seventy percent of the specimens were accounted for by one collection of 5490 specimens of the clupeid Etrumeus teres at OS02, in winter. The other tow taken at this station in winter contained 943 specimens, 779 of which were E. teres. Of the remaining samples, none contained over 160 specimens and only three had more than 100. Twenty-five (69%) of the 36 samples contained fewer than 50 specimens and 10 (28%) had fewer than 15. Only one sample contained no fish (MS01, winter). Overall taxon composition and abundance by station and season are given in Appendix 17. Abundance is indicated by numbers of individuals per station. Although flow meter readings were recorded for each tow, values showed unreason- able variability, and thus standardized catch figures based on volume of water filtered were not calculated. Since all tows were of five minutes duration on the bottom, catches were assumed to be comparable. The five most abundant families of larval and juvenile fishes at each station are listed for winter in Table 6.18 and for summer in Table 6.19. Striking seasonal differences in family composition at each station probably reflect differences in spawning times of various species. Sciaenids (primarily Leiostomus xanthurus and Micropogonias undulatus), for instance, occurred at all stations during winter. This family was among the five most abundant families at every station except OS02 and OS03 and was the most abundant family at all three inshore stations. Spot and croaker are known to be winter spawners and were absent from all summer samples. Other families represented only in winter samples included Sparidae, Gadidae, Scophthalmidae, and Uranoscopidae. Families among the five most abundant at summer stations but which were absent or rare in winter samples include Engraulidae, Carangidae, Labridae, Chaetodontidae, Priacanthidae, Apogonidae, Scombridae, Gempylidae, Batrachoididae, Dactyloscopidae, Callionymidae, Carapidae, Antennariidae, and Cynoglossidae. A few families (Bothidae, Clupeidae, Gobiidae, and Serranidae) ranked among the most abundant at several stations in both winter and summer. Specimens ranged in size from 2 mm to 78 mm SL (Tables 6.20 and 6.21). Mean minimum and maximum lengths were 9.1 mm and 11.1 mm, respectively. As indicated by the average size and general morphology of the majority of specimens, the epibenthic sled collected primarily larval and postlarval forms. Only a few fully transformed juveniles were taken. Diversity, as indicated by number of taxa, was considerably higher in summer than in winter at inner and middle shelf stations (Tables 6.22 and 6.23). Mean number of taxa per tow at inner and middle shelf stations during summer was 13 and 15, respectively, versus means of five in both depth zones during winter. Seasonal diversity differences were not observed for outer shelf stations OS01 and OS03 where mean number of taxa per tow was 11 in winter and in summer. The highest diversity in both winter and summer occurred at OSO2. 213 Table 6*11* Abundance of fish species caught in rectangular Antillean traps during summer, 1980. n number of traps which caught fish, and N number of traps deployed and recovered. Station Species IS01 IS02 IS03 HS01 MS02 MS03 @g@-opristis ocTurus 3 Centropristis striate 11 6 11 Haemulon aurolineatum 2 1 Lutianus campechanus 1 PagnLs Zjj&rus 2 ON 2/2 2/4 1/2 0/2 0/2 2/2 Total number of fish 13 6 1 0 0 17 Catch per trap (n) 6.5 3.0 1.0 0.0 0.0 8.5 Total soak time(hrs) of n traps 2.3 1.6 0.7 0.0 0.0 1.7 Catch per hr of n traps 5.7 3.8 1.4 0.0 0.0 10.1 214 Table 6.18. Five most abundant families of larval and juvenile fishes collected by fish sled at.each station during winter, 1980. Percent of Total Station Family Total Number at Station ISM 1) Sciaenidae 11 36.7 2) Bothidae 8 26.7 3) Sparidae 3 10.0 4) Gadidae 2 6.7 Triglidae 2 6.7 Clupeidae 2 6.7 5) Gobiidae 1 3.3 Gobiosocidae 1 3.3 IS02 1) Sciaenidae 96 76.2 2) Bothidae 24 19.1 3) Gadidae 3 2.4 4) Gobiidae 2 1.6 5) Sparidae 1 0.8 IS03 1) Sciaenidae 19 90.5 2) Gobiidae 1 4.8 MS01 1) Bothidae 1 20.0 Sciaenidae 1 20.0 Stromateidae 1 20.0 Serranidae 1 20.0 Synodontidae 1 20.0 MS02 1) Bothidae 8 44.5 2) Sciaenidae 5 27.8 3) Clupeidae 4 22.2 4) Synodontidae 1 5.6 MS03 1) Clupeidae 21 38.9 2) Bothidae 15 27.8 3) Sciaenidae 6 11.1 4) Synodontidae 5 9.3 5) Serranidae 3 5.5 215 Table 6.1.8 (Continued) Percent of Total Station Family Total Number at Station OSO, 1) Clupeidae 87 64.0 2) Sciaenidae 17 12.5 3) Bothidae 14 10.3 4) Gobiidae 5 3.7 5) Serranidae 4 2.9 OS02 1) Clupeidae 6598 94.5 2) Bothidae 308 4.2 3) Stromateidae 75 1.1 4) Ophidiidae 69 0.9 5) Serranidae 34 0.5 OS03 1) Clupeidae 54 52.9 2) Synodontidae 7 6.9 Stromateidae 7 6.9 3) Myctophidae 5 5.0 4) Serranidae 3 3.0 5) Triglidae 3 2.9 t 216 Table 6.19. Five most abundant families of larval and juvenile fishes collected by fish sled at each station during susmser, 1980. Percent of Total Station Family Total Number at Station- I ISM 1) Engraulidae 50 51.6 2) Batrachoididae 12 12.4 3) Ophidiidae 7 7.2 4) Dactyloscopidae 5 5.2 Synodontidae 5 5.2 5) Gobiidae 4 4.1 CYnoglossidae 4 4.1 IS02 1) Clupeidae 32 17.2 2) Ratrachoididae 29 15.5 3) Gobiidse 26 13.9 4) Engraulidae 18 9.6 5) Carangidae 14 7.5 IS03 1) Gobiidae 8 17.8 2) Engraulidae 7 15.6 3) Serranidae 5 11.1 4) Callionymidae 4 8.9 5) Clupeidae 4 8.8 MS01 1) Cynoglossidae 23 29.5 2) Serranidae 14 18.0 3) Gobiidae 11 14.1 4) Callionymidae 8 10.3 5) Clupeidae 4 5.1 Carangidae 4 5.1 MS02 1) Bothidae 15 22.1 2) Ophidiidae 11 16.2 3) Engraulidse 7 10.3 4) Labridae 6 8.8 5) Synodontidae 5 7.4 217 Table 6.19 (Continued) Percent of Total Station Family Total Number at Station MS03 1) Clupeidae 170 59.0 2) Cynoglossidae, 28 9.7 3) Callionymidae 23 8.0 4)Bothidae 19 6.8 5) Carangidae 14 4.8 Osol 1) Bothidae 5 20.0 2) Apogonidae 4 16.0 Scombridae 4 16.0 3) Gobiidae 2 8.0 Cynoglossidae 2 8.0 4) Clupeidae 1 4.0 Labridse 1 4.0 Stromateidae 1 4.0 Priacanthidae 1 4.0 Chaetodontidae 1 4.0 Gempylidae 1 4.0 Serranidae 1 4.0 Carapidae 1 4.0 OS02 1) Myctophidae 7 12.7 2) Clupaidae 6 10.9 3) Antennariidae 4 7.3 4) Carangidae 4 7.2 5) Bothidae 3 5.4 Serranidae 3 5.4 Engraulidae 3 5.4 Scombridae 3 5.4 OS03 1) Bothidae 22 33.4 2) Myctophidae 12 18.2 3) Gobiidae 7 10.6 4) Engraulidae 4 6.1 5) Gonostomatidae 4 6.0 t 218 Table 6.20. Average (i) minimum and maximum values and range of standard length (SL) for larval and juvenile fishes collected in winter, 1980. R minimum i maximum Taxa len2th ( SL) length (mm SL) Ranite C-m-mSL) Congridae 13.5 13.5 6-21 C@hichthidae 9.0 44.0 6-59 Etrumeus teres 7.3 19.6 4-24 Sardinella aurita 10.0 17.0 10-17 Sardinella app. 8.0 13.5 7-14 Brevoortia spp. 8.2 12.5 5-13 Synodontidae 7.6 9.7 3-15 Aulopidae 11.0 11.0 11 Myctophidae 4.7 5.7 4-6 Diaphus spp. 6.0 6.5 4-8 Lampadena sp. 4.0 4.0 4 Myctophum spp. 7.0 9.5 6-12 Myctophinae 7.0 8.0 7-8 Gobiesox strumosus 11.0 11.0 11 Bregmacerotidae 7.5 12.5 7-15 Bregmaceros spp. 6.0 29.0 6-29 Urophycis regia. 15 .0 18.3 4-28 Urophycis spp. 11.3 11.7 3-27 Ophidiidae 12.4 16.0 3-24 Carapidae 30.0 30.0 30 Echiodon spp. 84.0 84.0 84 Syngnathus spp. 21.7 29.7 11-35 Scorpaenidae 5.0 5.0 4-6 Triglidae 4.8 6.0 4-7 Prionotus carolinus 30.0 42.0 30-42 Centropristis ocyurus 8.8 11.4 3-13 Centropristis spp. 4.0 5.0 4-5 Serranus spp. 4.0 5.0 4-5 Diplectrum spp. 7.0 9.0 4-13 Serraninae 6.0 6.7 3-9 Hemanthias spp. 4.7 5.0 4-6 Pomatomus saltatrix 8.0 8.0 8 219 Table 6.20 (Continued) I minimum R maximum Taxa length Omi SQ length (mm St) Range (mrn SL) Carangidae 4.0 5.0 4-7 Corypha na spp. 6.0 6.0 6 Gerreidae 7.0 7.0 5-9 Haemulidae 6.0 6.0 6 Sparidae 6.0 7.2 4-10 Pagrus pagrus 4.0 7.0 4-7 Stenoto us spp. 16.5 16.5 16-17 Leiostomus xanthurus 5.4 8.0 1-13 Micropogonias undulatus 6.2 6.8 4-10 Larimus fasciatus 3.0 3.0 3 Labridae 4.0 11.0 4-11 Scaridae 7.5 10.5 6-11 Uranoscopidae 4.0 4.3 3-6 Callionr,nidae 5.0 6.o 4-8 Gobiidae 7.4 10.8 4-17 Gobiosoms ginsburgi 18.0 18.0 18 Trichiurus lepturus 10.0 10.0 8-12 Cubiceps pauciradiatus 5.0 8.0 5-8 Psenes spp. 5.0 5.0 5 Peprilus spp. 4.2 5.5 3-7 Ariomma spp. 4.0 4.0 4 Hyperogl@phe spp. 4.0 9.0 4-9 Scophthalmus aguosus 5.2 7.8 3-11 Etropus jrimosus 6.2 10.2 4-14 Etropus spp. 4.5 15.2 3-30 Citharicithys arctifrons 15.0 15.0 15 Cithariclithys spp. 6.6 11.2 3-14 Cyclopse:ta fimbriata 4.5 4.5 3-6 Paralich:hys spp. 7.0 8.0 6-10 Bothus spp. 14.7 15.7 11-19 Soleidae 4.0 4.0 4 Svmphuru;'spp. 4.5 7.0 4-10 220 Table 6.20 (Continued) R minimum i maximum Taxa length (mm SL) length (mm SL) Range (wn SL) Monacanthus spp. 4aO 4.0 4 T- Tetraodontidae 2.0 2.0 2 Other fish larvae 3.3 4.0 3-4 Disintegrated fish 3.0 6.0 3-6 unidentifiable 221 Table 6.21. Average (ic) minimum and maximum values and range of standard length (SL) for larval and juvenile fishes collected in summer, 1980. R minimum R maximum Taxa lenitth (mm SQ length (mm_EL) Rance (mm SL) Nessorh 3Lmphus spp. 7.0 8.0 7-8 Congridae 6.0 6.0 6 Ophichthidae 44.7 44.7 8-78 Clupeidae 9.0 9.0 9 Sardinella aurita 7.2 11.2 5-19 Engraulj.dae 7.2 15.2 5-30 Gonostomatidae 10.5 10.5 B-13 Cycloth,ne spp, 6.0 6.0 6 Mauroli@us spp. 5.0 7.0 5-7 Vincigu!rria spp. 13.0 13.0 13 Synodontidae 9.0 18.0 5-34 Synodus poeyi 26.0 26.0 26 Myctophidae 5.0 8.5 4-10 Forichtiys plectrodon 17.0 22.8 17-26 Antennariidae 3.0 3.0 3 Bregmac ros spp. 4.0 4.0 4 Ophidiidae 11.8 19.4 4-37 Lepophi ium spp. 35.7 35.7 26@-55 Carapus bermudensis 22.0 22.0 22 Echiodon.spp. 73.0 73.0 73 Exocoetidae 13.0 13.0 3-30 Hippoca pus erectus 6.0 6.0 6 Scorpaenidae 3.7 4.7 2-6 Triglidae 4.2 5.2 3-8 Prionot-s spp. - 3.0 6.0 3-6 Serraniculus pumilio 3.0 6.0 3-6 Serranus.phoebe 17.0 17.0 17 Serranus spp. 4.0 4.0 4 Diplectrum spp. 7.7 9.4 3-12 Serraninae 3.5 4.5 3-8 Anthias spp. 6.0 6.0 6 Priacanthidae 3.0 3.0 3 222 Table 6.21 (Continued) R min imum R maximum Taxa length (mm SL) length (mm SL) Range (mm SL) I Apogonidae 12.0 12.0 5-19 Apogon quadrisquamatus 10.0 10.0 10 Apogon aurolineatus 13.5 13.5 13-14 Apogon pseudomaculatus 25.7 30.7 21-35 Pomatomus saltatrix 4.0 4.0 4 Carangidae 3.0 3.7 2-5 Decapterus punctatus 14.5 15.0 3-30 Decapterus spp. 4.0 4.0 4 Selene setapinnis 3.0 3.0 3 Seriola spp. 3.0 3.0 3 Lutjanidae 3.0 3.o 3 Rhomboplites aurorubens 10.0 10.0 8-12 Gerreidae 10.5 10.5 10-11 Haemulidae 5.5 6.0 5-7 Holacanthus spp. 4.0 4.0 4 Chromis enchrysurus 29.0 29.0 29 Labridae 7.4 8.4 5-12 Halichoeres bivittatus 29.0 29.0 29 Scaridae 9.0 9.0 9 Opistognathidae 5.0 5.0 5 Dactyloscopus spp. 10.0 10.0 10 Blenniidae 5.0 5.0 5 Hypleurochilus geminatus 11.4 12.4 6-19 Clinidae 5.0 9.5 5-10 Callionymidae 3.3 5.0 3-9 Gobiidae 7.5 11.6 4-21 Evermannichthys spongicola 12.0 17.0 12-17 Lythrypnus phorellus 11.0 11.0 11 Gempylidae 8.0 8.0 8 Sco mbridae 5.0 5.0 5 Euthynnus alletteratus 5.4 6.2 4-9 Scomberomorus cavalla 7.0 7.0 7 223 Table 6.21 (Continued) R minimum R maximum Taxa length (mm SL) length (mm SO Ranite (mm SO Euthynn,s pelamis 5.0 5.0 5 Auxis sl 6.0 6.0 6 )p Cubicep;. pauciradiatus 6.0 6.0 6 Psenes iiellucidus 5.0 5.0 5 Ariomma spp. 4.5 4.5 4-5 Etropus crossotus 3-0 5.0 3-5 Etropus spp. 7.6 9.9 3-14 Citharichthys spilopterus 7.0 7.0 7 Citharichthys.gymnorhinus 11.0 11.0 11 Cithari hthys spp. 7.8 9.7 4-15 Cyclopsetta fimbriata 4.0 4.0 4 Bothus spp. 11.2 13.2 4-20 Syacium spp. 4.2 6.5 3-10 Soleidae 5.0 5.0 5 Symphur s spp. 5.8 10.5 3-17 Monacanthus hispidus 12.0 14.0 6-20 Monacanthus SPP. 3.0 3.0 3 Aluterus sp 9.0 9.0 9 p Sphoeroides spp. 3.0 3.0 3 Other fish larvae 3.5 3.5 3-4 Disintegrated fish unidentifiable 224 Table 6.22. Number of individuals and number of taxa of larval and juvenile fishes in fish sled collections, winter 1980. Collection Number Number Station Number Individuals Taxa I I ISM 800066 26 9 800067 4 3 IS02 800142 79 5 800143 47 8 IS03 800102 14 3 800103 7 3 MS01 800227 5 5 MS02 800188 5 1 800189 13 5 MS03 800403 8 4 800404 46 9 Osol 800315 70 9 800316 66 11 OS02 800330 943 40 800331 6373 47 OS03 800382 67 16 800383 35 8 225 Table El.@13. Numbers of individuals and number of taxa of larval and juvenile fishes in fish sled collections, summer 1980. Collection Number Number Station Number Individuals Taxa ISM 800471 58 14 800472 39 9 IS02 800511 81 16 800512 106 19 IS03 800534 23 13 800535 22 9 MS01 800624 44 12 800625 34 11 MS02 800557 31 17 800558 37 14 MS03 800646 157 21 800647 131 13 Osol 800764 8 6 800765 17 12 OS02 800726 12 7 800727 43 25 OS03 800671 31 15 800672 35 13 226 Numbers of taxa taken in the two tows at OS02 in winter (40 and 47) were more than twice those taken at any other station in winter or summer. A major objective of the epibenthic fish sled sampling was to determine how extensively live bottom habitats may be used as nursery grounds by fishes designated as priority species due to their commercial importance. Of the seven priority species, only two (R. aurorubens and P. pagrus were repre- sented in sled samples and these by only two specimens each (Figure 6.28). DISCUSSION Intensive studies directed at live bottom fish assessment have not been published. Published trawl studies have dealt with open shelf sand bottom habitat or on the results of exploratory fishing not specifically directed at live bottom. Species composition, abundance, and distribution patterns of the dominant demersal fishes reported herein are consistent with those reported in the available literature (Struhsaker 1969, Miller and Richards 1979, Wenner et al. 1980). Comparison with open shelf studies shows greater abundance, biomass, and diversity of fishes in live bottom habitats. The dominant species Stenotomus aculeatus, Haemulon aurolineatum, and Calamus leucosteus are ubiquitous species which are found in a wide range of habitats but which are more abundant on and near live bottom (Struhsaker 1969, Waltz et al. in preparation, Manooch and Barans in preparation). For example, total catch of S. aculeatus in six trawls at MS02, a live bottom area, exceeded total cat-ch in 40 trawls in similar depths and season over the open shelf (Wenner et al. 1980). Calamus leucosteus was also much more abundant than reported from sand bottom trawls. The occurrence of H. auroli- neatum over sand bottom (Wenner et al. 1980) may be related to fee behavior, since many haemulids, including H. aurolineatum, are known to forage at night over sand flats, returning to the reef during the day (Randall 1963, Collette and Talbot 1972, Parrish and Zimmerman 1977). The most noteworthy difference in abundance of dominant species between the North Carolina live bottom site and those areas trawled off of South Carolina and Georgia, is the differing abundance of vermilion snapper (Rhomboplites aurorubens). This priority species was a dominant species at all three middle shelf stations off South Carolina and Georgia in summer. Trawl collections at those three stations produced a mean of 350 individuals per station. In con- trast, only two individuals were caught in the trawl at the middle shelf station off North Carolina. Grimes et al. (1977) noted that vermilion snapper appeared to increase in abundance from northern Onslow Bay, North Carolina south to South Carolina waters. Biomass estimates from trawl catches indicate that biomass of demersal teleosts and total nekton is much higher on live bottom than on the open shelf. Wenner et al. (1980) reported mean values of 12.372 and 3.070 kg ha-l for total nektonic and demersal teleost biomass, respectively, from 70 trawls over sand bottom in the South Atlantic Bight (9 - 366 m depth in summer). M Tan biomass from summer trawls in the present study was 46.580 and 30.974 kg ha- for total nekton and demersal teleosts, respectively. Biomass estimates from live bottom collections off North Carolina were slightly higher - 58.354 and 35.237 kg ha-1. (See Volume II, Chapter Six.) Powles and Barans (1980) reported fish biomass of 27.3 kg ha-l on live bottom, based on their largest 227 34* 800 South Carolina *Rhombopfites ourorubens +Pagrus.pagrus *Luijanidoe ..CHARLESTON--. *OISOI SAVANNAH OMSOI *OSOl 820 *OMS02 Georgia 32* OIS02 -,@-OOS02 (2) BRUN ICK *OMS03 OOS03 OIS03 JACKSONVILLLE.'.*. 800 Figure 6.28. Collection locations for larval and juvenile priority fish species captured by fish sled. 228 trawl catches. Fish biomass estimated from trawl collections on live bottom areas in the South Atlantic Bight is considerably less than the 490 kg ha-1 estimated by Bardach (1959) or 446 kg ha-1 estimated by Odum and Odum (1955) for tropical reefs in the western Atlantic (Bermuda) and central Pacific, respectively. Biomass on artificial reefs in the tropical western Atlantic has been estimated at 680 kg ha-1 in the Florida Keys and 6980 kg ha-1 in the Virjin Islands (Stone et al. 1979). The biomass estimates calculated from trawl catches should be considered minimum estimates because vulnerability and availability of the fishes captured are unknown (Edwards 1968). The estimates obtained from natural reefs and artificial reefs in the tropics are from visual counts in clear water, or from poison collections, and this could account for part of the higher biomass estimated by those authors. Bardach (1959) compared his reef fish biomass estimates to estimates from New England and the northeast Atlantic and concluded that higher temperatures and increased surface area pro- vided by reefs accounted for higher biomass. The lower relief, cooler and more variable temperature, and the patchy nature of live bottom areas in the South Atlantic Bight could also account for the lower biomass estimates in the present study, compared to tropical reefs. The significant differences in biomass between stations in winter were due to the very low biomass of demersal teleosts at IS01 and IS02 and the high biomass at MS02. As inner shelf waters warmed during summer, biomass at IS01 and IS02 increased as fishes apparently moved into these areas from warmer offshore waters, and there was no significant difference between stations in summer. Middle shelf live bottom areas supported the greatest biomass (kg ha-1) of demersal teleosts. Miller and Richards (1979) noted similar conclusions and attributed the high productivity of these depths to seasonal thermal stability. Diversity values for demersal fishes were low relative to invertebrate diversity (Chapter 5) due to the lower species richness and the numerical dominance of the community by a few species. Diversity values for the live bottom site off North Carolina (middle shelf) were similar to values at comparable depths off South Carolina and Georgia. Wenner et al. (1980) reported similar ranges of H' for individual trawl collections over sand bottom in the South Atlantic Bight in the same depths, with maximum values being higher at their inner and middle shelf sites but slightly lower at outer shelf sites. Foell and Musick (1979) reported a lower range of diversity values for trawl collections at depths of 39 - 73 m in the Middle Atlantic Bight. The higher diversity of demersal shelf fishes in the South Atlantic Bight (versus the outer shelf north of Cape Hatteras) is due to increased species richness. Whereas Foell and Musick (1979) reported 41 species in 264 trawl collections over four seasons, the 83 collections over two seasons in the present study produced 128 species. Wenner et al. (1980) collected 152 demersal species on the open shelf and slope in summer; however, their stations included a broader latitudinal and depth range in the South Atlantic Bight . The most noteworthy pattern in diversity at all live bottom sites, including the site off North Carolina, was the increased'diversity of collections made at night. Differences in diversity between light phases, depth zones, and between seasons within a depth zone appeared to be related to changes in community dominance or, alternatively, to changes in species richness. Thus, although species richness remained the same or increased at inner shelf stations in summer, H' diversity decreased because of the dominance of the community by one or two 229 species. Community dominance did not increase as much in summer at middle shelf sites, and diversity increased at those depths in summer because of increased species richness. Community dominance was low during both seasons at OS01, and increased species richness during summer resulted in a higher H' diversity. Increased H' diversity values in trawl collections made at night were also related to increased species richness. Several fish species demonstrated marked diel differences in abundance in trawl. catchesb4; Although this could be due to visual net avoidance, there is some evidence for real changes in the live bottom fish community between day and night. All Apogon pseudomaculatus were trawled at night. This is a nocturnal species with well developed vision for feeding at night (Livingston 1971) and could probably visually avoid the trawl during day or night. Members of the genus Apogon are known to hide in crevices during the day and to forage in the water column over and at the edges of reefs at night (Hobson 1965, Livingston 1971, Collette and Talbot 1972, Luckhurst and Luckhurst 1978). This behavior would make them susceptible to capture only at night. Equetus umbrosus was also captured exclusively at night. Although no habitat informa- tion is available for this species, closely related Equetus acuminatus and Equetus (= Pareques) viola are known to remain under ledges and in caves during the day, emerging into the open at night (Longley and Hildebrand 1941, Hobson 1965). Equetus umbrosus apparently has a similar behavior pattern and is captured at night when it comes out to feed. Several other species appeared to be noctur- nally active and thus vulnerable to the trawl at night (e*.g. Group A, Figures 6.24 and 6.27). Space is considered to be the limiting resource on tropical reefs, and diel changes in space utilization by coral reef fishes have been proposed as a mechanism for allowing a diverse community to occupy the same limited habitat (Smith and Tyler 1972, Luckhurst and Luckhurst 1978). Space is probably also a limiting resource on:live bottom areas, and diel movements-into and out of the reef may be a mechanism for partitioning this resource. Some species (e.g. P. carolinus and U. regia) generally associated with other ha@bitats such as sand or mud, were abundant in night tows over live bottom. These species may move into reef areas to rest or feed at night. More extensive food habits studies are needed to fully understand these diel abundance patterns. The results of cluster analysis indicate that the demersal fish fauna of live bottoms on the shelf consists of an inner shelf component, a shelf break component, and a middle shelf component composed of unique species plus species shared with the inner shelf and shelf break. The inner shelf is the most unstable thermally and is characterized by the greatest fluctuation in communit, composition and overall abundance. Many species found at inner shelf stations were not faithful during both seasons, and dominant species changed dramatically. This was particularly true at the two northernmost inner shelf stations, which had the widest seasonal temperature difference (110C at IS01 and 16.10C at IS02). In winter, these stations were characterized by few fishes and by temperate species (e.g. Urophycis 12_&ia) which moved offshore to cooler water in summer. In summer, warm temperate and subtropical species invaded these area (e.g. Haemulon aurolineatum, Apogon pseudomaculatus, Monacanthus hispidus and these two stations were similar in fAunal composition to middle shelf statiops. Station IIS03 had fewer seasonal d-ifferences in species composition and abundance. This is probably due to its more southerly position and its lower seasonal tem- perature difference ( 90C). 230 Miller and Richards (1979) suggested that the middle shelf (18 - 55 m) in the South Atlantic Bight is the most thermally stable zone. They reported subtropical fish species in this zone with a center of distribution and maximum abundance of commercial species at 33 - 40 m. In the present study, fish abundance was also higher at middle shelf sites and did not vary as much between seasons as did inner shelf sites. Nodal analysis indicated a hJgh affinity of dominant subtropical species (e.g. Lutjanus campechanus, Equetus lanceolatus, Holacanthus bermudensis, Mycteroperca microlepis) for middle shelf stations. With the exception of Centropristis striata, all priority (i.e. commercially important) species were more abundant in trawl catches at middle shelf depths. Most species faithful to middle shelf stations were faithful in both winter and summer. Species that changed fidelity seasonally either moved to or from shallow or deeper water as suggested by Miller and Richards (1979). Thus, Pagrus pagrus was in a species group which was highly faithful to MS02 in winter, but belonged to a group highly faithful to OS01 in summer. Outer shelf hard bottom areas are characterized by unstable temperatures due to cold water intrusions (Miller and Richards 1979). No species in the group faithful to OS01 in winter were included in the group faithful to that station in summer, indicating the thermal instability of that station. -The present study indicates four major species assemblages at the outer shelf station: (1) ubiquitous species that range across the shelf (Rhomboplit@Ls aurorubens, Calamus leucosteus), (2) temperate species that move in from deeper water in winter (Urophycis regia), (3) subtropical species that invade these depths from shallower water in summer (Equetus umbrosus), and (4) species which have their major abundances at these depths year-round [Equetus (= Pareques sp. nov., Serranus phoebe, Chaetodon aya, Chaetodon sedentarius]. Miller and Richards (109) notW-similar'results. Species composition of the fish fauna as seen by the television camera differed from that captured by the trawl. One reason for this is the inability to accurately identify many fishes on the television monitor, whereas most fishes captured by trawl were identified to species. Many of the unidentified fishes on videotapes are probably species commonly caught in the trawl (e.g. S. aculeatus, H. aurolineatum, R. aurorubens). In addition, the narrow field of view of the camera (approximately 3.4 m) records fewer of the most abundant species captured by the trawl. Another reason for the faunal difference in trawl collections versus television observations is that many fishes seen on videotapes, particularly large species, may avoid the trawl. Abundance of red snapper, groupers, sheepshead,black sea bass, and greater amberjack was greater, based on videotape analysis, than trawl collections indicated. For example, large amberjacks (Seriola dumerili) were rarely taken by trawl at any station, and only one was 7@a-ken at middle shelf depths in the summer (< 1 individual ha-l of swept area). In contrast, video- tape analysis indicated a density of 96.6 individuals ha-l at the same stations. Differences in abundance estimates for these fishes (Table 6.11) between television (and diver observations) and trawl collections are probably due to the ability of these large fishes to avoid the trawl. Estimates of overall fish abundance also differed between traw-i samples, television transects,* and diver observations, with no consistent pattern to the differences. Uzmann et al. (1977) and Powles and Barans (1980) reported estimates of fish density obtained from underwater television that were 231 generally higher than those obtained by trawl, and this was generally true in the present study. Baited fishing gear has only limited utility as a method of assessing fish abundance, but the present data provides useful comparisons with other studies. Vertical longlines deployed in the Virgin Islands caught a maximum of 0.04 fish per hook per minute (Olsen et al. 1974). Maximum catches in the present study wete considerably lower, 0.004 fish per hook per minute. Powles and Barans (1980) reported catches in summer of from 3.0 (day) to 20.0 (night) fish hr-l for Antillean S-traps on the South Atlantic Bight middle shelf. In the present study, summer catches at middle shelf stations were lower (1.2 - 8.6 fish1hr-1), although comparable catches were made in winter (2.7 - 21.2 fish hr- ). Maximum catches for Antillean S-traps and rectangular Antillean traps were 21.2 and 5.7 fish hr-1, respectively. Antillean S-traps were more effective at catching fish than the rectangular design traps. The low abundance or absence of priority species in fish sled samples was most likely due to (1) sampling periods not coinciding with known spawning periods of these species, (2) avoidance of the sled by postlarvae and juveniles or (3) the possibility that larvae and juveniles of priority species are not associated with live bottom habitat. For example, no Centropristis larvae which could be positively identified as C. striata were caught by the sled. The absence of C. striata from winter and summer samples is not surprising because C. striata spawns from' March to May off the Carolinas (Cupka et al. 1973, Mercer 1978),with a peak in April. Thus, few if any larvae would have been present before completion of the winter sampling in mid-March. Furthermore, Kendall (1972) suggested that C. striata larvae are pelagic until approximately 13 mm. Even specimens spawned in late February would probably not have reached that size and thus would not have been available to the epibenthic sled. Individuals spawned as late as May or June would have grown large enough (at least 30 mm) to easily avoid the sled by early August, when simmer sampling began. April - May sampling would be necessary to verify the use of live bottom habitat by young C. striata. However, if Kendall's (1972) estimate of the size at settling is correct, avoidance of the sled even by newly settled individuals is likely. Only two Pagrus pagrus larvae (4 - 7 mm) were taken in the sled. This is particularly surprising in light of Ranzi's (1969) observation that these larvae occur in the deep plankton until they reach about 10 mm, at which time the- ly migrate to the surface. The small, deep-living individ- y apparent uals may not actually be bottom associated, but water column samplers seem to be no more efficient at capturing Pagrus larvae. Of approximately 100,000 fish larvae collected during two years of seasonal sampling with neuston and bongo nets throughout the South Atlantic Bight (Powles 1977), only 14 speci- mens were identified as P. pagrus; all were taken with the neuston net at the surface, and the majority were larger than 10 mm. Ripe females of P. pagrus have been collected off North Carolina from January -through April in depths from 21 to 100 m. Peak spawning (based on capture of ripe individuals) was reported to occur from March through April off North Carolina (Manooch 1976) and probably occurs about a month earlier off South Carolina (W. A. Roumillat, pers, comm., S. C. Marine Resources Center, Charleston; 1981). Thus, larvae should have been relatively abundant during at least the latter part of the winter sampling period. In light of the abundance of adult P. pagrus throughout the Bight, the rarity of its 232 larvae remains an enigma. There is no indication from epibenthic sled sampling that larval or postlarval P. pagrus are preferentially associated with live bottom areas. First year juvenile P. pagrus may inhabit live bottom areas, but this question cannot be answer7e-d- with the present sampling gear. Ranzi (1969) indicated that settling occurs at lengths above 20 mm, again a size not likely to be sampled by the sled. The largest collection of juvenile P. pagrus taken in seven years of MARMAP trawl sampling off the Southeast United States (44 specimens, 42 - 59 mm SQ was taken in relatively shallow water (9 - 20 m) over flat sand bottom. Two specimens of vermilion snapper, Rhomboplites aurorubens, were taken in the epibentic sled during the summer sampling period; a 12 mm specimen at ISOI and an 8 mm specimen at MS02. These samples were taken during what is probably a period of peak abundance of R. aurorubens larvae (August - I September) (Grimes 1976, LaRoche 1977, Powles 1977). The capture of only two specimens suggests that vermilion snapper larvae and postlarvae are not significantly concentrated near the bottom in live bottom areas. LaRoche (1977) found specimens as large as 14 mm in the water column. No Lut.anus campechanus larvae were taken in the epibenthic sled, despite the fact that summer samples were taken well within the suspected spawning period and probably near peak activity (Beaumariage and Bulloch 1976, G. D. Johnson, pers. comm., S. C. Marine Resources Center, Charleston, 1981). If young red snapper preferentially inhabit live bottom areas, residence apparently begins above sizes at which avoidance of the sled is possible. Because larvae of this species have only recently been described (Collins et al. 1980) records from previous surveys are nonexistent. No larval, postlarval, or juvenile groupers (Mycteroperca microlepis, M. phenax. or Epinephelus niveatus) were collected by the epibenthic sled. Gag and scamp, M. microlepis and M. phenax, spawn from January to April with peak spawning off the Carolinas from February to April, and snowy grouper spawn in late summer and early fall (McErlean 1963, Presley 1970, unpubl. MARMAP data, S. C. Marine Resources Center, Charleston, 1979 - 1981). Larval gag remain planktonic and enter estuaries where juveniles spend 6 to 8 months of their first year. Consequently, their absence from sled samples is not sur- prising. Juvenile scamp and snowy grouper, however, have been collected on live bottom (unpubl. MARMAP data, S. C. MarineResources Center, Charleston, 1979 1981; H. R. Beatty, pers. comm., S. C. Marine Resources Center, Charleston, 1981). Their absence from epibenthic sled samples is most likely a reflection of their large size at settling and their cryptic habits. Increased larval fish diversity in epibenthic sled collections in summer is clearly attributable to the spring-summer peak in spawning for most fishes in the area. Fahay (1975) noted a similar summer increase in larval fish diversity in surface towed metre net collections. Hydrographic conditions at OS02 in winter and the exceptionally high diversity of larval fishes there are characteristic of Gulf Stream waters. This increased diversity is attributable to northward transport of larvae from more southern areas where spawning seasons of a more diverse fauna are generally protracted, and to the occurrence of deep water pelagic species such as gonostomatids, myctophids and deep sea eels. The striking influence of Gulf Stream intrusions on taxon composition at OS02 points out the ephemeral nature of the ichthyoplankton community even near the bottom. A significant 233 portion of larvae sampled by the epibenthic sled may be transitory and not directly tied to the live bottom habitat. IMPACT/ENHANCEMENT Potential ii3pact to fish populations in live bottom habitats might result from the drilling process and from oil spills. Discharge of drill cuttings and drilling mud, and drilling itself may cause destruction of habitat and smothering mortality of benthic epifauna. Although fishes are highly mobile and may avoid localized areas of disturbance, many reef fishes (e.g., Rhombop ites aurorubens, Lutjanus campechanus, many pomacentrids, chaetodontids, and various groupers) are sedentary in habit and do not move off their home reef (Bardach 1958, Randall 1962, Smith and Tyler 1973, Gladfelter and'Glad- felter 1978, Luckhurst and Luckhurst 1978, Fable 1980). Also, many live bottom fishes feed directly on live bottom associated epifauna and would be adversely affected by any resultant lowered food density. (See Chapter 7 for a more detailed discussion.) Acute effects of oil spills could result in direct physical harm to fishes, such as coating of gill membranes and sensory structures, which could lead to immediate mortality (Heitz et al. 1974, Corner et al. 1976). Fish eggs, larvae, and juveniles are particularly susceptible to the more volatile components of crude oil (Corner et al. 1976, Sharp et al. 1979). Because the early life history stages of many species (e.g., P. pagrus) frequently occur in the upper water column and are often found at @_he surface, they would be readily exposed to the more toxic, volatile components of a spill. Sublethal effects due to chronic exposure to oil pollution include increased oxygen consumption (Thomas and Rice 1979), reduced development rates (Sharp et al. 1979), and interference with sensory initiated behavior such as feeding (see Cha-ter 7) and reproduction (Corner et al. 1976). Oil spills can also reduce the commercial value of a fishery without direct mortality to the fish by imparting unpleasant odors and flavors to fish flesh, thereby making commercial species unsalable (Johannes 1975, Corner et al. 1976). Petroleum spills and drilling operations may also adversely affect fishes by introducing toxic concentrations of trace metals into the environment. Be- cause trace metals naturally occur in very low concentrations in seawater and carbonate sediments associated with live bottom, introduction of these sub- stances through oil development would expose fishes to much higher concentra- tions than they are normally accustomed (Johannes 1975, Bryan 1976). These high concentrations of trace metals can be directly lethal to fishes, especially larval stages (Waldichuk 1974), and sublethal effects can also be deleterious. For example, high concentrations of trace metals, such as zinc, damage gill structures in fishes (Waldichuk 1974, Hughes 1976). Sublethal concentrations of mercury and cadmium reduce fecundity of female fishes and fertility of spermatozoa in males (Waldichuk 1974). Additionally, through bioaccumulation and food web magnification, top level predators of commercial importance can become tainted and thus unmarketable. Another potential disturbance to fish populations is the noise resulting from drilling and production. Noise produced from such activities could frighten fish away from areas where platforms are located; however, there is little evidence to indicate this would happen. Numerous investigators 234 have attempted to scare fish using sounds, but with little success. Generally, the fish are initially startled but rapidly become accustomed to noise, in- cluding sounds of very high amplitude (Hawkins 1973). Higher ambient noise conditions caused by petroleum production can raise the response threshold level to specific sounds to which fishes normally react (Hawkins 1973). Many species of fishes associated with live bottom produce their own,species specific sounds (e.g., sciaenids, haemulids, batrachoidids, labrids, scarids). In many families of fishes (e.g., Batrachoididae, Gadidae, Brotulidae, Ophidiidae, Macrouridae, Sciaenidae) the sounds produced and the structures associated with sound production are sexually dimorphic and are used in court- ship and reproduction (Hawkins 1973, Fine 1975). Noise caused by oil produc- tion activity might inhibit reproduction in those species by raising the threshold level of response to reproductive sounds to a point above the sound producing ability of the fish. Further studies are needed to determine the effect of the frequency and amplitude of sounds produced by petroleum production on behavior in fishes. Inner shelf stations vary seasonally in fish species composition and abundance, but support large populations of fishes in summer, including recreationally (and easily accessible to sportfishermen) and commercially important species (e.g., black sea bass, sheepshead). Because some of the fishes of these areas apparently move offshore during winter, they may be able to avoid local disturbances and could return to a disturbed area the next season if the environment recovered. Middle shelf stations have more environ- mental stability and support greater concentrations of commercially valuable fish (red porgy, red snapper, gag, scamp, whitebone porgy). Because of this stability, disturbance in the form of drilling and oil spills might have a greater effect on fish community structure of these areas. The middle shelf is also the most likely area for gas and oil development on the shelf off Georgia and South Carolina based on the past lease sale, and particular care should be taken in developing these areas. The outer continental shelf and shelf break support populations of red snapper, grouper (various species), and tilefish which are currently exploited commercially. Adverse effects of oil development could have an economic impact on these fisheries. There is some evidence that oil development may enhance finfish popula- tions on the South Atlantic Bight shelf. Drilling platforms could provide additional living space and food for some species in the form of attached epifauna. These resources, especially suitable living space, may be limited on the South Atlantic shelf, and, in this respect, drilling platforms could function as artificial reefs. In addition, pelagic "baitfish" are known to be attracted to artificial structures for behavioral reasons (Klima and Wickham 1971) and would provide additional food for large predatory species. CONCLUSIONS - Most demersal shelf fishes demonstrated large seasonal differences in abundance at each station, but especially at inner and outer shelf stations. This is most likely due to the thermal instability of inner and outer shelf waters. All priority species except black sea bass (Centropristis striata) were most abundant at middle shelf stations. Centropristis striata was most abundant at inner shelf stations. 235 Diversity (H') values for demersal fishes ranged from 0.8 (MS02, winter) to 3.2 (OS010 summer) and are comparable to values reported for similar depths from sand bottom in the South Atlantic Bight and live bottom off of North Carolina. Diversity was higher at night versus day and was higher in winter than summer at-inner and outer shelf stations, but lower in winter at middle shelf stations. Species richness was higher in summer than in winter at most stations, but 14' diversity patterns appeared to be more closely related to community dominance. - Mean biomass per tow for all stations combined was greater in summer than in winter. There were no significant differences in mean biomass per tow between stations in summer. In winter, middle shelf stations had signifi- cantly greater biomass than inner or outer shelf stations. Biomass esti- mates from the live bottom areas studied were considerably higher than those estimates given in the literature for sand bottom areas in the South Atlantic Bight. Estimated biomass of fishes from the live bottom site off North Carolina was slightly higher than that estimated from sites off South Carolina and Georgia. - Cluster analysis demonstrated striking differences in community composition between day and night tows. Also evident were seasonal changes in species composition at inner and outer shelf stations, and greater seasonal community stability on the middle shelf. - Underwater television and diver observations provided useful complementary data to trawl collections, and documented the abundance of snappers, groupers, and other larger fishes at middle shelf stations. Underwater television was also useful for assessing species composition and abundance of fishes at stations which could not be trawled. Baited fishing gears were not as effective as the trawl in catching priority fish species. These gears confirmed distribution and abundance patterns of priority species as evaluated from trawl catches. They also were useful in confirming the presence of priority species at stations which could not be trawled. Antillean S-traps yielded the greatest number of individuals per hour of fishing. The larval and juvenile fish sled did not collect many priority fishes, and was not useful in assessing the importance of live bottom as spawning and nursery areas for those species. The sled most effectively samples larval and postlarval fishes, rather than juveniles. The offshore oil drilling process and possible oil spills may cause localized areas of reduced fish abundance. Because the middle shelf has the highest biomass and abundance of fishes, including many economically valuable species, particu- lar care should be taken in developing middle shelf live bottom areas. f Drilling rigs and production platforms may provide additional food and shelter for fishes through the creation of artificial reefs, and this could increase fish production in the South Atlantic Bight. 236 CHAPTER 7 FOOD HABITS OF FISHES INTRODUCTION Live bottom areas support a greater abundance, diversity, and biomass of fishes than adjacent areas of the open shelf (see Chapter 6). Many economically important fishes are found associated with live bottom habitats and currently support active commercial and recreational fisheries in the South Atlantic Bight. The dependence of these economically important fishes on live bottom for food and shelter is poorly understood. Although food habits information is available for some species of fishes associated with live bottom (Bradley and Bryan 1975, Manooch 1977, Grimes 1979, Link 1980), those studies have not examined the importance of live bottom habitat as feeding grounds for fishes, nor have they examined diet overlap of the species studied with other fishes in the community. The purpose of this chapter is to describe the seasonal food habits of seven priority and ecologically dominant live bottom fish species, to evaluate dependence on live bottom as feeding grounds by these species, and to relate the food habits of these species to prey and predator community structure. METHODS Laboratory Analysis: Initially, seven fish species were proposed as priority species for study: Centropristis striata, Epinephelus niveatus, Lutjanus campechanus, Mycte operca microlepis, M. phenax, Pagrus pagrus, and Rhomboplites aurorubens. Epine helus niveatus and M. phenax were not collected by any sampling gear and were not included in the analysis. Two additional species were substituted. Stenotomus aculeatus was chosen because it was the most abundant species collected (Chapter 6). Calamus leucosteus was also chosen because of its abundance over live bottoms (Chapter 6) and importance in the trawl fishery (Waltz et al. in preparation), and for comparison with other dominant sparids, P. pagrus and S. aculeatus. Fixed stom-achs were washed in tap water and transferred to 50% isopropanol in the laboratory. Attempts were made to examine at least 10 stomachs per station per season for each priority species, 5 from day trawls and 5 from night trawls. When sufficient numbers were not available in trawl collections, stomachs were also utilized from collections made with other gears (traps, longlines, snapper reels). Stomachs analyzed were randomly selected from those preserved when more than 10 stomachs were available. Stomach contents were sorted to the lowest possible taxon and counted. Colonial forms and fragments of animals were counted as one organism, unless abundance could be estimated by counting pairs of eyes (crustaceans), otoliths (fishes), or other parts. Any prey items ( i.e., fish or cephalopod remains) that might have been bait on passive fishing gears were not included in the analysis. Volume displacement 237 of food items was measured using a graduated cylinder, or estimated by using a 0.1-cm2 grid (Windell 1971). Data Analysis: Methods of food habits quantification are variously biased (Hynes 1950, Pinkas et al. 1971, Windell 1971); therefore, the relative contribution of different food items to the total diet of each species was determined using three methods: (1) the number of stomachs in which a food item occurred was expressed as a percent frequency occurrence (F), i.e., a percentage of the total number of stomachs containing food; (2) the number of individuals of each type of food was expressed as percent numerical abundance (N), i.e., a percentage of the total number of food items from all stomachs; and (3) the volume displacement of a food item was expressed as percent volume displacement (V), i.e., a percentage of the total volume of food from all stomachs. From these, an index of relative importance, IRI (Pinkas et al. 1971), was calcu- lated for each prey species and higher taxon as follows: IRI = (N + V) F where N, V, and F are the numerical, volumetric, and frequency percentages as defined above. This index has proven useful in evaluating the relative importance of different food items found in fish stomachs (Pinkas et al. 1971, McEachran et al. 1976, Sedberry 1980), and was used in the present study to describe the food habits of each species and determine seasonal differences in the relative importance of food items. Similarity in diet between predators was measured using the Bray-Curtis measure (Bray and Curtis 1957), expressed as: S 1 - i X jk ki@ Z (X ji + Xki) i where Sik is the similarity between the predators j and k; Xii is the abundance of the ith prey taxon (the lowest level to which t e prey was identified) for predator j; and Xki is the abundance of the ith prey taxon for predator k. Because sample sizes were unequal, abundance of prey items was standardized as percent numerical abundance for each predator (Clifford and Stephenson 1975, Boesch 1977). Similarity values were presented in trellis diagrams. Overlap in diet among all predators was also measured using numerical classification techniques (cluster analysis) for comparison with other studies which have used this technique. Each predator was treated as a collection, and all predators were subjected to normal cluster analysis based on the Bray-Curtis similarity measure as defined above. Similarity among groups of predators was expressed in the form of dendrogram's generated using flexible sorting with a = -.025 (Lance and Williams 1967a, Clifford and Stephenson 1975). To determine the dependence of priority species on live bottom organisms for food, percent volume of prey species consumed by each predator 238 was separated into habitat components (live bottom, sand bottom, or water column), based on information from the literature. Percent volume was used because it is acloser estimate of energy content than frequency or number. RESULT'S Of the 790 stomachs from seven fish species examined, 509 (39.2%) contained food. Results from the analysis of these stomachs are presented below in individual species accounts. Centropristis striata: The contents of 250 black sea bass stomachs examined varied with season. During winter, amphipods were the most abundant prey, especially Erichthonius brasiliensis and caprellids (Figure 7.1 and Table 7.1). Fishes and decapods were most important volumetrically. Brachyurans, particularly Pilumnus sayi, were the most important decapods. Most fish remains were impossible to identify, but Sardinella aurita was an important species. Summer food habits differed from winter primarily in the reduced importance of amphipods as prey. Caprellid amphipods, which were abundant in the diet in winter, were not consumed in summer. Pilummus sayi was still the most important decapod, and many planktonic Lucifer faxoni were also consumed. Several fish species were important in the (fi@etin summer. Most were small juveniles which were also abundant in trawl catches in the summer. Ascidians, ophiuroids, polychaetes, and other taxa were also consumed. Pagrus pagrus: The contents of 183 stomachs of red porgy varied little between seasons at the higher taxonomic levels, and fishes, decapods, and polychaetes were the most important foods during both seasons (Figure 7.2). Amphipods and anthozoans (Actiniaria) were of lesser importance. Numerous other taxa were infrequently consumed (Table 7.2). Although relative abundance of higher taxa was similar seasonally, the species consumed varied between winter and summer. Clupeids and seahorses (HippocampuEsp.) were the most important fish in winter but were not consumed in surnaer. Several brachyuran species were consumed in winter, but crabs were infrequent decapods in the diet in summer. Rhomboplites aurorubens; Contents of vermilion snapper stomachs (N = 142) varied greatly with season (Figure 7.3). In winter, several taxa were important in the diet. Cumaceans, ostracods, and amphipods were the most important higher taxa, and decapods and fishes were volumetrically important. Oxyurostylis smithi, the Most important prey species (Table 7.3), is a sand dwelling cumacean. Cumaceans are known to swarm in the water column at night (Anger and Valentin 1976), and R. aurorubens may have fed on them at that time. Ostracoda A, the second most important prey species, is a planktonic form. Promysis atlantica and Phtisica marinal like 0. smithi, are partially planktonic. Other planktonic prey included @-a-la-noid copepods and decapod larvae. 239 Cel?frOPHSAS SWO(7 100- WINTER 1980 TAXON A AMPHIPODA 6224 so- 9 DECAPODA 2533 C PISCES 396 - D OPHIUROIDEA 33 E ISOPODA 32 w 60- F POLYCHAETA I I G PORIFERA 3 H ASCIDIACEA I z 40- 20 C D E FG 0-- w 20- 0 > 40- L So- so SUMMER 1980 A 27 8 43ST Cc Go- C 2907 w D 74 E 3 F 51 40- z G 45 20- C H 92 -A D E F G H 0- - w 20- 0 >40- Go- % FREQUENCY W@"-) Figure 7.1. Frequency, number, volume (percents) and index of relative importance (IRI-) of higher taxonomic groups of food in the diet of Centropristis striata. 240 lable 7.1. Percent frequency occurrence (F), percent number (N), percent volume M, and index of relative importance (IRI) of food items in Centropristis striata stomachs for both sampling periods. tr trace volume. 4 Winter 1980 Summer 1980 Food Itesh F N V IRI F N V RI Foraminifers Unidentified Foraminifers 1.16 0.09 .01 <1 Porifera Unidentified Porifera 1.16 0.04 2.78 3 9.09 3.33 1.61 45 Cnidaria Hydrozoa Aglaophenia trifida 4.65 0.17 0.05 1 Campanulariidae 1.16 0.04 0.01 <1 Unidentified Hydrozoa 1.51 0.56 0.01 1 Total Hydrozos 5.81 0.22 0.06 2 1.52 0.56 0.01 1 Anthozo:o,..,Ji. Octo 1.16 0.04 0.01 <1 Telesto fruticulosa 1.16 0.04 0.01 <1 Telesto sp. 1.51 0.56 0.07 1 Total Anthozoa 2.33 0.09 0.02 <1 1.52 0.56 0.07 1 Annelids Polychaeta Ampharete americans 1.16 0.04 0.02 <1 Aphrodite hastata 1.51 0.56 0.07 1 Aphroditidae ? 1.51 0.56 0.29 1 Notopygos crinita 1.51 0.56 0.07 1 Phyllodoce groenlandica 1.51 0.56 0.05 1 E. longipes 1.16 0.04 0.02 <1 Polynoidae 1.16 0.04 0.19 <1 Unidentified Polychaeta 4.65 0.17 0.87 5 3.03 1.11 1.79 9 Total Polychaeta 8.14 0.30 1.09 11 9.09 3.33 2.28 51 Molluscs Gastropods Calliostoma sp. 1.16 0.04 0.01 <1 Marginella hartleyanum 1.51 0.56 tr. 1 Mitrella lunata 1.16 0.04 0.01 <1 Natica pusilla 1.51 2.22 tr. 3 Olividae 1.16 0.04 0.01 <1 Total Gastropods 3.49 0.13 0.03 1 3.03 2.78 0.01 8 Pelecypoda Laevicardium pictuth 1.51 0.56 0.10 1 Musculus lateralis 1.16 0.04 0.03 <1 Pteria colymbus 3.49 0.22 0.03 1 Semele purpurascens 3.03 2.22 0.32 8 Total Pelecypoda 4.65 0.26 0.06 1 4.55 2.78 0.42 15 Cephalopoda Loliginidae 1.16 0.04 0.14 <1 3.03 1.11 6.97 24 Crustacea Copepoda Labidocera aestiva 1.16 0.61 0.03 1 Cirripedia Balanus trigonus 2.33 0.09 0.30 1 CC=acea Cyclaspis varians 1.51 0.56 tr. 1 urostylis smithi 2.33 0.17 0.02 <1 Total Cumacea 2.33 0.17 0.02 <1 1.52 0.56 tr. I Isopoda Carpias bermudensis 4.65 0.61 0.03 3 Cirolana polita 2.33 0.35 0.10 1 241 Table 7.1 (Continued) Winter 1980 Summer 1980 F N v IRf F N v IRI Paracerceis caudats 10.46 0.39 0.32 7 3.03 1.11 0.01 3 Unidentified Isopoda 1.16 0.04 tr. @l Total Isopoda 17.44 1.39 0.45 32 3.03 1.11 0.01 3 Amphipoda Gammaridea Ampelisca sp. 1.16 0.09 0.01 <1 A. agassizi 1.16 0.09 0.01 <1 A. vadorum 3.49 0.17 0.03 1 A. verrilli 1.51 1.11 tr. 2 Ceradocus sp. 1.51 0.56 tr. I Cerapus tubularis 4.65 0.48 0.04 2 Elasmopus sp. A 1.16 0.04 0.02 <1 Erichthonius brasiliensis 40.70 41.51 1.69 1758 Leucothoe spinicarpa 2.33 0.09 0.02 <1 1.51 0.56 tr. I Listriella clymenellae 1.16 0.04 0.01 <1 Lysianassa sp. 1.51 0.56 0.01 1 Lysianassidae 1.16 0.04 0.02 <1 Lysianopsis alba 2.33 0.09 0.02 <1 1.51 0.56 tr. I Melita appendiculata q.30 0.52 0.16 6 Microdeutopus sp. 1.16 0.04 0.01 <1 Microlassa sp. 2.33 0.09 0.01 <1 Photis sp. 1.16 0.04 tr. <1 .E. puRnator 15.12 2.31 0.17 37 Podoceridae 1.16 0.04 0.01 <1 Podocerus sp. 5.81 0.35 0.05 2 Polycheria sp. 1.16 0.04 0.01 <1 Stenothoe sp. A 1.16 0.04 0.01 <1 1. georgiana 15.12 1.00 0.10 17 Trichophoxus floridanus 1.16 0.04 0.01 <1 Unidentified Gammaridea 9.30 1.00 0.08 10 1.51 1.11 tr. 2 Caprellidea Caprella penantis 2.33 0.26 0.03 1 Caprellidae 12.79 15.55 1.30 215 Caprella equilibra 31.39 21.82 2.84 774 Luconacia incerta 12.79 1.22 0.19 18 Phtisica marina 1.16 0.04 0.01 <1 Total Amphipoda, 66.28 87.06 6.84 6224 6.06 4.44 0.02 27 Mysidicea Bowmaniella vortoricensis 1.51 0.56 tr. I Unidentified -Mysidicea 1.16 0.52 0.04 1 Total Mysidacea 1.16 0.52 0.04 1 1.52 0.56 tr. 1 Decapoda Natantia Hippolytidae 1.16 0.04 0.02 <1 Leptochela sp. 2.33 0.09 0.10 <1 L. papulata 2.33 0.09 0.15 1 Lucifer faxoni 9.09 11.67 0.03 106 Neopontonides beaufortensis 4.65 0.35 0.12 2 Periclimenes sp. 1.16 0.04 0.05 <1 P. longicaudatus 3.49 0.26 0.10 1 3.03 1.67 0.06 5 Processa bermudensis 3.03 1.11 0.01 3 Sicyonia brevirostris 4.54 1.67 5.60 33 S. typica 3.03 1.11 0.82 6 Synalpheus longicarpus 3.03 1.11 0.25 4 Synalpheus townsendi 3.49 0.22 0.20 1 1.51 0.56 0.00 1 Thor sp. 2.33 0.61 0.11 2 1.51 0.56 tr. 1 T. floridanus 2.33 0.13 0.04 <1 T. manningi 1.16 0.09 0.03 <1 I Unidentified Natantia 11.63 1.05 0.42 17 7.57 2.78' 0.05 21 Reptantia Macrura Scyllarus chacei 1.51 0.56 1.45 3 242 Table 7.1 (Continued) Winter 1980 Summer 1980 F N V IRI F N V -FRI Anomura Albunea paretti 1.16 0.04 3.15 4 Dardanus fusosus 1.16 0.04 3.98 5 Galathea rostrata 1.51 1.11 0.05 2 Paguridae 3.49 0.13 0.06 1 1.51 0.56 tr. 1 Pagurus sp. 2.33 0.09 0.08 <1 9.09 4.44 0.12 41 P. carolinensis 3.49 0..13 0.11 1 6.06 2.22 0.03 14 P. hendersoni 3.03 1.11 0.03 3 Brachyura lappa angusta 3.03 1.11 2.57 11 Dromedia antillensis 1.16 0.04 0.28 <1 Hexapanopeus sp. 1.51 0.56 0.19 1 i!. angustifrons 3.03 1.11 0.46 5 Macrocoeloma camptocerum 1.16 0.04 0.37 <1 1.51 0.56 0.03 1 Majidae 1.16 0.04 0.01 <1 Hicropanope sp. 1.16 0.04 0.02 <1 Hithrax sp. 3.03 1.11 0.24 4 !j. hispidus 1.16 0.04 0.19 <1 j!. pleuracanthus 3.49 0.13 4.15 15 Ovalipes sp. 1.16 0.04 0.01 <1 0. stephensoni 1.16 0.04 2.32 3 0. stephensoni? 1.16 0.09 1.09 1 Pelia mutica 3.49 0.17 0.33 2 ]Eil-@-U--P- 4.54 1.67 0.25 9 P. floridanus 1.51 0.56 0.44 2 P. sayi 4.65 0.43 12.18 59 21.21 7.78 6.49 303 Pinnotheres maculatus zoea 1.16 1.26 0.04 2 Pitho Iherminieri 1.16 0.04 0.20 <1 3.03 1.11 0.41 5 Podochela gracilipes 1.51 0.56 0.03 1 P. riisei 6.98 0.30 1.77 14 1.51 0.56 0.14 1 Stenorhynchus seticornis 1.16 0.04 0.93 1 1.51 1.11 0.23 2 Xanthidae 2.33 0.09 0.13 <1 1.51 0.56 0.07 1 Brachyuran megalopae 1.16 0.04 0.01 <1 Unidentified Brachyura 15.12 0.65 6.31 105 Decapoda larvae 1.16 0.09 0.01 <1 Unidentified Decapoda 2.33 0.09 0.16 1 Total Decapoda 54.65 7.14 39.21 2533 62.12 50.56 20.07 4387 Sipunculida Sipunculus nudus 1.16 0.04 0.60 1 Ectoprocta Diaperoecia floridana 1.16 0.04 0.01 <1 1.51 0.56 tr. 1 Discoporella umbellata 1.16 0.04 0.02 <1 Unidentified Ectoprocta 1.51 0.56 0.05 1 Total Ectoprocta 2.33 0.09 0.03 <1 3.03 1.11 0.05 4 J,chinodermata Ophiuroldea Unidentified Ophiuroidea 18.60 1.00 0.77 33 12.12 5.55 0.52 74 Holothuroidea Unidentified Holothuroidea 2.33 0.09 4.81 11 3.03 1.11 1.70 8 ".'hordata Ascidiacea Ascidiacea? 1.16 0.04 0.18 <1 Diplosoma macdonaldi? 3.03 1.11 4.12 16 Styela plicata 1.51 0.56 1.70 3 Unidentified Ascidiacea 1.16 0.04 0.23 <1 4.54 1.67 0.92 12 Total Ascidiacea 2.33 0.09 0.41 1 9.09 3.33 6.73 92 Cephalochordata Branchiostoma caribaeum 1.16 0.04 0.05 <1 243 Table 7.1 (Continued) Winter 1980 Sumer 1980 F N v IRI F N v IRI Pisces Carangidae 1.51 0.56 0.73 2 Decapterus punctatis 3.03 1.67 6.35 24 Haemulon aurolineatum 4.54 3.33 4.75 37 Labridae 1.16 0.04 1.67 2 Porichthys plectrodon 3.03 1.11 14.05 46 RhomboplItes aurorubens 1.51 0.56 27.62 43 Sardinella aurita 1.16 0.09 3.33 4 1.51 0.56 0.07 1 Synodontidae 3.03 1.11 1.96 9 Urophycis regia 1.16 0.13 0.69 1 Unidentified Teleostei 5.81 0.22 36.58 214 22.73 8.33 4.01 281 Total Pisces 9.30 0.48 42.17 398 37.88 17.22 59.52 2907 Number of stomachs examiu-ted 142 98 Examined stomachs with food 86 66 244 pagras pagrus -so- WINTER 1980 TAXON APISCES 3282 BDECAPODA 1446 w CPOLYCHAETA 508 40- DAMPHIPODA 149 M EANTHOZOA 71 z FCEPMALOCMORDATA 47 20- A 6ECHINOIDEA 6 E F 0-- - - - - - - - - - - 20- w 2 D -j 40- 0 ae 60- SUMMER 1980 ZRI A 1137 a 1845 C 1146 w 40- D 44 E 02 B I C F 128 z 20- G 173 A 0 E F G 0- - - - - - - - - -- 20- w 40- 0 > 8@0 % FREQUENCY Figure 7.2. Frequency, number, volume (percents) and index of relative importance (IRI) of higher taxonomic groups of food in the diet of Pagrus pagrus. 245 Table 7.2. Percent frequency occurrence (F), percent number (N), percent volume (V), and index of relative importance (IRI) of food items in Pagrus pagrus stomachs for both sampling periods. tr - trace volume. Taxon Winter 1980 S,-r 1980 Food Item F N V IRI F N V IRI Foraminifers Unidentified Foraminifers 3.13 1.11 0.03 4 Porifera Unidentified Porifera 4.69 1.11 2.48 17 Cnidaria Hydrozoa Salacia desmoidds 1.56 0.37 0.01 1 Anthozoa Actiniaria 7.81 2.20 4.66 54 6.25 3.08 13.23 102 Unidentified Anthozoa 1.56 0.37 0.28 1 Total Anthozoa 9.38 2.58 4.95 71 6.25 3.08 13.23 102 Annelids Polychaeta Aphrodita hastata 3.13 1.54 10.05 36 Chaetopteridae 3.13 1.54 0.02 5 Eunice sp. 1.56 0.37 0.28 1 3.13 1.54 0.14 5 E. antennata 1.56 0.37 0.04 1 E. websteri 3.13 3.08 0.46 11 Glycera americans 1.56 0.37 0.04 1 Lumbrineridae 3.13 1.54 0.07 5 Lumbrineris sp. 3.13 1.54 0.23 6 Nereidae 1.56 0.37 0.01 1 Notopygos crinita 3.13 1.10 0.32 4 3.13 1.54 0.07 5 Dnuphidae 1.56 0.37 0.07 1 Oauphis eremita 1.56 0.37 0.14 1 0. nebulosa 9.38 2.20 0.69 27 3.13 1.54 0.34 6 @&ien-iafusiformis 1.56 0.37 0.14 1 Sabellidae 3.13 0.73 0.28 3 Serpulidae 1.56 0.73 0.14 1 3.13 1.54 tr. 5 Sigalionidae 3.13 0.73 0.70 4 Syllidae 1.56 0.37 0.14 1 Syllis regulata carolinae 1.56 0.37 0.01 1 Terebellidae 3.13 1.54 0.07 5 Unidentified Polychaeta 9.38 2.20 0.69 27 9.38 4.61 0.37 47 Total Polychaeta 34.38 11.07 3.72 508 34.38 21.54 11.81 1146 Molluscs Gastropods Naticidae 3.13 0.73 0.15 3 Unidentified Gastropods 3.13 0.73 0.11 3 Total Gastropods 6.25 1.48 0.27 11 Scaphopoda Dentaliidae 1.56 0.37 0.01 1 Cephalopoda Loligo plei 3.13 1.54 7.99 30 Crustacea Ostracoda Ostracoda A 1.56 1.11 0.01 2 Copepoda Unidentified Copepoda 1.56 0.37 0.01 1 3.13 1.54 tr. 5 Cirripedia Balanus sp. 1.56 1.84 0.03 3 1.54 0.02 5 .E. trigonus 3.13 16.54 1.99 58 3.13 Total Cirripedia 3.13 18.45 2.01 64 3.13 1.@4 0.02 5 246 Table 7.2 (Continued) Winter 1980 Summer 1980 Amphipoda- F N v IRI F N v IRI Gammaridea AmpelisKa verrilli 3.13 1.54 0.02 5 Erichtksbnius brasiliensis 3.13 0.73 0.03 2 Lilleborgia sp. 1.56 0.37 0.01 1 Melita appendiculata 1.56 0.37 0.01 1 Unciola sp. 1.56 0.37 0.01 1 Unidentified Gammaridea 3.13 0.73 0.03 2 3.13 1.54 tr. 5 Caprellidea Phtisica marina 9.38 7.72 0.18 74 3.13 1.54 0.02 5 Total Amphipoda 14.06 1-0.33 0.28 149 9.38 4.62 0.05 44 MysIdacea Bowmaniella portoricensis 10.94 2.95 0.20 34 Decapoda Natantia Alpheidae 1.56 0.73 0.01 1 Alpheus normanni 3.13 1.54 a.ii 5 Leptochela sp. 1.56 0.37 0.01 1 papulata 10.94 3.68 0.46 45 9.38 4.61 0.64 49 Periclimenaeus ? sp. 3.13. 3.08 0.05 10 Processa bermudensis 1.56 0.37 0.04 1 Synalpheus townsendi 3.13 0.73 0.10 3 6.25 3.08 0.27 21 Thor sp. 3.13 0.73 0.03 2 Unidentified Natantia 12.50 4.04 0.76 60 6.25 3.08 0.98 25 Reptantia Anomura Albunea gibbesii 5.13 1.54 10.96 39 Paguridae 1.56 0.37 0.03 1 Pagurus sp. 3.13 1.54 0.11 5 P. carolinensis 3.13 0.73 0.06 2 B:r-achyura Calappa sp. 1.56 0.37 0.82 2 Macrocoeloma camktocerum 1.56 0.37 0.56 1 Majidae, 4.69 1.47 2.41 18 Metoporhaphis calcarata 1.56 0.37 0.92 2 Mithrax pleuracarithus 3.13 1.54 2.72 13 Osachila sp. 1.56 0.37 0.28 1 Parapinnixa bouvieri 3.13 0.73 0.28 3 Parthenope P. 1.56 0 37 0 28 1 P. fraterculus 1.56 0:37 0:01 1 Portunus sp. 3.13 1.54 0.05 5 P. anceps 1.56 0.37 0.80 2 Ranilia muricata 1.56 0.37 0.14 1 3.13 3.08 1.37 14 Unidentified Brathyura 12.50 3.31 1.65 62 3.13 1.54 0.46 6 Decapoda zoea 3.13 1.54 tr. 5 Total Decapoda 48.44 20.22 9.65 1446 40.63 27.69 17.73 1845 Unidentified Crustacea 3.13 1.54 0.02 5 Ectoprocta Diaperoecia floridana 7.81 1.84 0.10 15 3.13 1.54 tr. 5 Discoporella umbellata 1.56 0.37 0.01 1 Parasmittina trispinosa 1.56 0.37 0.01 1 Total Ectoprocta 9.38 2.58 0.13 25 3.13 1.54 tr. 5 Echinodermata Ophiuroidea Unidentified Ophiuroidea 10.94 2.58 0.51 34 9.38 4.62 0.48 48 Echinoidea Arbacia puncculata 3.13 1.54 1.90 11 Encope sp. 3.13 1.54 5.30 21 Eucidaris tribuloides 3.13 1.54 0.23 6 Lytechinus variegatus 1.56 0.37 0.01 1 Stylocidaris affinis 3.13 1.54 0.27 6 Unidentified Echinoidea 3.13 0.73 0.13 3 Total Echinoidea 4.69 1.11 0.14 6 12.50 6.15 7.70 173 247 Table 7.2 (Continued) Winter 1980 Summer 1980 F N v IRI F N v IRI Holothuroidea Unidentified Holthuroidea 1.56 0.37 1.69 3 Chordata Ascidiacea Unidentified Ascidiacea 3.13 0.74 4.83 17 Cephalochordata Branchiostoma caribaeum 7.81 4.78 1.25 47 9.38 12.31 1.32 128 Pisces Bothidae 1.56 1.10 0.85 3 Clupeidae 4.69 1.10 29.23 142 Decapterus punctatus 3.13 1.54 2.74 13 Etrumeus teres 1.56 2.20 0.28 4 Hippocampus sp. 6.25 5.15 6.83 75 Ogcocephalidae 1.56 0.37 0.30 1 Ophidiidae 1.56 0.37 0.25 1 Rhomboplites aurorubens 3.13 1.54 9.14 33 Rhomboplites aurorubens? 3.13 1.54 14.82 51 Stenotomus sp. 1.56 0.37 10.14 16 Synodus poeyi 3.13 3.08 11.42 45 Fish scales 1.56 0.37 0.01 1 Unidentified Teleostei 20.31 5.15 19.89 509 9.38 4.61 1.53 58 Total Pisces 39.06 16.24 67.79 3282 21.88 12.31 39.65 1137 Total number of stomachs examined 119 64 Examined stomachs with food 64 32 248 Rhomboplites Ourorubens 130- -WINTER 1980 TAXON IRI - A CUMACEA 2035 B OSTRACODA 1056 60- j C AMPHIPODA 848 0 DECAPODA 720 - E MISIDACtA 647 F PISCES 422 40- 6 4COPEPODA 286 z - A 20- E C D F G 0__ w 20 j j5 40- 60- so- 60- SUMMER 1980 IRI A 0 a 23 C sit so- 0 689 w E 27 cc F 911 40- G 659 z 20- C D -a E IF 0- - - - - - - - - - - - - 20- D _j 0 40- > - L____j 60- 001 % FREQUENCY (401%) Figure 7 .3. Frequency, number, volume (percents) and index of relative importance (IRI) of higher taxonomic groups of food in the diet of Rhomboplites aurorubens. 249 Table 7.3. Percent frequency occurrence (F) , percent number (N) , percent volume M, and index of relative importance (IRI) of food items in Rhomboplites aurorubens stomachs for both sampling periods. tr trace volume. Taxon Winter 1980 Summer 1980 Food Item F N V IRI F N V IRI Annelids Polychaeta Eunicidae 2.27 0.21 7.71 18 Phyllodoce longipes 18.18 1.59 6.32 144 Unidentified Polychaeta 3.28 0.68 0.63 4 Total Po2ychaeta 20.45 1.80 14.03 324 3.28 0.68 0.63 4 Molluscs Gastropods Natics pusilla 6.56 5.82 0.80 43 Naticidae 2.27 0.11 0.20 1 Naticidae A 2.27 0.21 0.99 3 Thecosomata 1.64 0.34 0.17 1 Unidentified Gastropods 1.64 0.68 0.11 1 Total Gastropods 4.55 0.32 1.19 7 8.20 6.85 1.08 65 Pelecypoda Ervilia concentrica 4.92 4.45 0.17 23 Cephalopoda Loliginidae 1.64 0.34 22.17 37 Crustacea Ostracoda Ostracoda A 25.00 38.10 4.15 1056 4.92 2.05 0.06 11 Unidentified Ostracoda 3.28 0.68 tr. 2 Total Ostracoda 25-00 38.10 4.15 1056 8.20 2.74 0.06 23 Copepoda Candacia curta 6.82 1.06 0.59 11 1.64 0.34 tr. I Coacaeus sp. 2.27 0.21 0.20 1 Labidocera aestiva 9.09 0.74 0.79 14 Nannocalanus minor 2.27 0.11 tr. <1 Temora stylifera 6.82 0.32 0.20 4 T. turbinata 13.64 1.59 0.79 32 22.95 19.52 0.28 454 'Un4-inulavulgaris 1.64 0.34 tr. 1 Cal4noida 6.82 0.42 0.40 6 4.92 3.08 0.06 is Total Copepoda 38.64 4.45 2.96 286 27.87 23.29 0.34 659 Stomatopoda Stomatopoda larvae 1.64 0.34 0.06 1 Unidentified Stomatopoda 1.64 0.34 0.57 1 Total Stomatopoda 3.28 0.68 0.63 4 Cumacea Cyclaspis varians 15.91 1.80 1.98 60 Oxyurostylis smithi 38.64 21.90 16.80 1495 Unidentified Cumacea 27.27 1.90 2.77 127 Total Cumacea 43.18 25.60 21.55 2035 Amphipoda G-ridea Ampelisca agassizi 2.27 0.11 0.20 1 A. vadorum 2.27 0.11 0.20 1 Bachyporeia parkerl 2.27 0.11 0.20 1 Corophiidae 1.64 0.68 0.06 1 Lystanopsis alba 2.27 0.11 0.40 1 1.64 0.34 tr. 1 Microdeutopus sp. 2.27 0.11 0.20 1 Photis sp. 4.54 0.21 0.40 3 Protomedia sp 2.27 0.21 0.20 1 AM@ @[email protected] 6.82 0.32 0.59 6 Tiron tropakis 4.54 0.21 0.40 3 1.64 0.34 tr. 1 Unidentified Gammaridea 9.09 0.42 1.38 16 3.28 l.P3 0.06 4 250 Table 7.3 (Continued) Winter 1980 Sun=r 1980 F N V IRY F N V IRI Caprellidea Caprellidae 2.27 0 11 0.20 1 Luconacia incerta 2.27 0:11 0.20 1 Phtisica marina 27.27 4.34 3.95 226 3.28 1.37 0.06 5 Hyperiidea Hyperiidae 9.09 0.63 0.59 11 4.92 1.03 0.28 6 Lestrigonus bengalensis 9.84 7.53 0.40 78 Lycaea sp. 3.28 0.68 0.06 2 Phronima sp. 4.92 1.03 1.71 13 Simorhynchotus.sp. 1.64 0.34 0.06 1 Unidentified Hyperiidea 3.28 0.68 tr. 2 Iotal Amphipoda 52.27 7.11 9.11 848 34.43 15.07 2.67 611 Mysidacea Bowmaniella portoricensis 11.36 1.06 1.98 34 8.20 2.05 0.34 20 Mysidopsis bigelowi 6.82 0.32 0.79 8 M. furca 2.27 0.11 0.20 1 Tr atlantica 11.36 14.29 8.50 259 Unidentified Mysidacea 6.82 0.42 0.79 8 1.64 0.34 0.06 1 Total Mysidacea 22.73 16.20 12.25 647 9.84 2.40 0.40 27 Decapoda Natantia Alpheidae zoea 4.54 0.21 tr. 1 Leptochela sp. 1.64 0.34 0.23 1 .L. papulata 2.27 0.11 0.20 1 9.84 3.08 2.27 53 Lucifer faxoni 14.75 5.48 0.45 88 Ogyrides sp. 2.27 0.11 0.20 1 Sicyonia typica 1.64 0.34 0.06 1 Synalpheus townsendi 2.27 0.11 0.59 2 Natantia larvae 2.27 0.11 0.20 1 Unidentified Natantia 15.91 1.16 9.88 176 6.56 1.71 0.23 13 Reptantia Macrura Panulirus sp. larvae 1.64 0.34 0.06 1 Anomura Paguridae zoea 1.64 0.68 tr. 1 Porcellanidae zoea 2.27 0.11 0.20 1 Anomura zoea 2.27 0.11 0.20 1 Brachyura Calappidae megalopae 1.64 0.34 0.11 1 Dromidia antillensis 2.27 0.11 0.20 1 Hypoconcha sp. 1.64 0.34 0.11 1 Portunus sp. 1.64 0.34 0.28 1 Xanthidae megalopae 1.64 0.34 tr. 1 Xanthidae zoea 2.27 0.21 0.20 1 Brachyura zoea 4.54 0.32 0.40 3 1.64 0.68 tr. 1 Unidentified Brachyura 2.27 0.11 2.57 6 1.64 0.68 0.45 2 Decapoda zoea 4.92 1.03 tr. 5 Total Decapoda 40.91 2.78 14.82 720 34.43 15.75 4.26 689 Unidentified Crustacea 18.03 19.52 14.27 609 Chaetognatha Unidentified Chaetognatha 13.64 1.37 1.98 46 13-11 4.45 0.63 67 Chordata Cephalochordata Branchiostoma caribaeum 6.82 1.16 0.59 12 1.64 0.34 0.57 1 Pisces Fish scales 9.09 0.42 0.59 9 3.28 0.68 tr. 2 Unidentified Teleostei 13.64 0.74 16.80 239 13.11 2.74 52.13 720 Total Pi:ces 22.73 1.16 17.39 422 16.39 3.42 52.13 911 Number of a omachs examined 59 83 Examined stomachs with food 44 61 251 The diet of vermilion snapper was quite different during summer, but again included many planktonic forms. Cumaceans and ostracods were of lesser importance in summer. Amphipods were nearly as important as in winter, but consisted mainly of planktonic hyperiids. Most decapods were also planktonic (e.g., Lucifer faxoni). Fishes were most important in the diet in summer and consisted mainly of small postlarval forms which could not be identified. Callamus leucosteus: Several higher taxa were frequently found in the 93 whitebone porgy stomachs examined (Figure 7.4). In winter, decapods, polychaetes, and gastropods were the most important prey taxa. Brachyurans and pagurids were the important decapods, and several different polychaete species were consumed in approximately equal numbers (Table 7.4). Identifiable gastropods were mostly naticids, which are usually found on sand bottom. In summer, decapods, polychaetes, and gastropods were again the most important prey, but gastropods were more important than polychaetes. Pagurids and brachyurans were again the most important decapods. Asteroids and pele- cypods, which were not consumed in winter, were occasionally eaten in summer. Stenotomus aculeatus: Contents of the 96 southern porgy stomachs examined varied seasonally. In winter, amphipods and polychaetes were the most important prey items (Figure 7.5). Live bottom species (Erichthonius brasiliensis, caprellids) were the most important amphipods, and the infaunal cephalochordate, Branchiostoma caribaeum, was also important in the diet (Table 7.5). Several polychaete species were of nearly equal importance, and Oxyurostylis smithi was the most important cumacean. Chaetognaths were relatively important in the winter diet and numerous other taxa were also consumed. In summer, pelecypods (primarily recently set Ervilia concentrica) replaced amphipods as the most important prey. Polychaetes@ were not as important as in winter, and fewer cumaceans were consumed. Copepods and ophiuroids remained relatively unimportant in the diet but were more frequently consumed in the summer. Sipunculids were also more frequently consumed in summer. Lutjanus campechanus: Red snapper were infrequently captured during both seasons, and food habits analysis was limited (31 stomachs). Fishes were the most important prey for L. campechanus (Figure 7.6). Few invertebrates were consumed (Table 7.6), and most were consumed by smaller red snapper. The fishes that were consumed were abundant demersal and pelagic species. Lutjanus campechanus is evidently a top carnivore that feeds on fish which are found on, or in the water column above live bottom. .Mycteroperca microlepis: Gag were very rarely captured by any gear (only 5 stomachs were collected), but are apparently common at middle shelf stations, based on diver observations. Gag, like red snapper, were top predators which fed mainly on fish (Table 7.7). The only identifiable fish remains were.Rhomboplites aurorubens, which is a very abundant live bottom species. 252 ca/amus latlcoste'vs TAXON IRI A DECAPODA 3046 8 POLYCHAETA 1649 Go- WINTER 1980 C GASTROPODA 1101 D AMPHIPODA 215 E SIPUNCULIDA le5 w 40 F ASTEROIDEA 0 (D A G PELECYPODA 0 H OPHIUROIDEA 183 z 20- C ag - D H 0 -- - - - - - - - - - - - - - w 20- 40- Goi 3:R1 60- SUMMER 1980 A 2803 a 745 C less w 40- D 99 CO C :E E 132 :3 A F 292 20- G 234 B H 202 G 0 F H 0 -- - - - - - - - - -- - - - - w - i i 20- 0 > 40- 60-1 % FREQUENCY ( -'0--"4) Figure 7.4. Frequency, number, volume (percents) and index of relative importance (IRI) of higher taxonomic groups of food in the diet of Calamus leucosteus. 253 Table 7.4. Percent frequency occurrence (F), percent number (N), percent volume M. and i-d x of re ative importance (IRI) of food items in Calamus leucosteus stomachs for both .::plina periods. tr - trace volume. Taxon Winter 198) Sumer 1980 Food Item F N V IRI F N V IRI Algae Bacillariophyceae 3.33 0.54 tr. 2 Porifera Unidentified Porifera 3.33 0.54 1.09 5 Cnidaria Anthozoa Actiniaria 11.43 2.10 6.34 96 3.33 0.54 3.26 13 Renilla reniformis 2.86 0.52 0.48 3 3.33 0.54 18.13 62 Total Anthozoa 14.29 2.63 6.81 135 6.67 1.09 21.39 150 Annelids Polychaeta Arabella iricolor 2.86 0.52 1.29 5 A. mutans 2.86 0.52 1.70 6 3.33 0.54 4.35 16 Capitellidae 2.86 0.52 0.48 3 Cirratulidae 6.67 1.09 1.09 14 Diopatra cuprea 2.86 0.52 2.86 10 Dodecaceria corallii 3.33 0.54 0.07 2 Glycera sp. 2.86 1.05 0.68 5 Lumbrineris coccinea 2.86 0.52 1.02 4 Maldanidae 2.86 0.52 0.68 3 3.33 1.09 2.18 11 Nephtyidae 6.67 1.09 0.15 8 Nereidae 2.86 0.52 0.07 2 Onuphis eremita 2.86 0.52 0.07 2 3.33 1.63 2.83 15 0. nebulosa 2.86 0.52 0.34 2 0. pallidula 2.86 0.52 0.34 2 Dpheliidae 3.33 0.54 0.07 2 Paranaitis polynoides 3.33 0.54 0.07 2 Petaloproctus socialis 2.86 0.52 0.20 2 Phyllodocidae 2.86 0.52 0.07 2 Scalibregmidae? 6.67 1.09 0.44 10 Sigalionidae 2.86 0.52 0.14 2 Spionidae 2.86 0.52 0.14 2 Sthenelais sp. 2.86 0.52 0.68 3 Syllidae 2.86 0.52 0.07 2 Terebellidae? 2.86 0.52 2.59 9 Travisia parva 2.86 0.52 0.14 2 Unidentified Polychaeta 25.71 5.26 2.72 205 10.00 2.17 0.80 30 Total Polychaeta 51.43 15.79 16.28 1649 33.33 10.33 12.04 745 Molluscs Gastropods Anachis avara 5.71 2.10 0.34 14 Epitoni sp. 3.33 10.33 0.36 36 E. multistriatum 2.86 0.52 tr. 2 Marginella sp. 3.33 0.54 0.44 3 Natica canrena 2.86 0.52 0.07 2 6.67 2.72 1.02 25 Naticidae B 2.86 0.52 0.20 2 Naticidae 6.67 3.80 0.22 27 Unidentified Gastropods 28.57 13.16 14.65 794 36.67 16.30 7.32 866 Total Gastropods 34.29 16.84 15.26 1101 43.33 33.70 9.35 1866 Pelecypoda Americardia media 3.33 0.54 0.07 2 Corbula dietziana 3.33 1.63 1.45 10 Tellina sp. 6.67 1.63 0.29 13 Unidentified Pelecypoda, 10.00 2.17 3.92 61 Total Pelecypoda 20.00 5.98 5.73 234 Cephalopoda Unidentified Cephalopoda 2.86 0.53 0.07 2 254 Table 7.4 (Continued) Winter 1980 Summer 1980 F N V IRI F N V IRI Crustacea Cirripedia Balanus sp. 10.00 1 63 0.22 18 )--u-" 6.67 1 09 1.02 14 -t r-'A B. venustus 6.67 1.09 0.36 10 Unidentified Cirripedia 2.86 1.58 3.41 14 Total Cirripedia 2.86 1.58 3.41 14 16.67 3.80 1.60 90 Cumacea Cyclaspia varians 2.86 0.52 tr. 2 Oxyurostylis smithi 17.14 4.21 0.20 76 Unidentified Cumacea 2.86 0.52 tr. 2 Total Cumacea 22.86 5.26 0.20 125 Amphipoda Gammaridea Ampelisca sp. 6.67 1.09 0.00 7 Ampelisca sp. A 3.33 0.54 0.15 2 A. agassizi 2.86 0.52 0.07 2 A. vadorum 2.86 0.52 0.07 2 Erichthonius sp. A 2.86 0.52 tr. 2 E. brasiliensis 2.86 0.52 tr. 2 iiaustoridae 5.71 1.05 0.07 6 Lembos unicornis 2.86 0.52 0.07 2 Tiron tropakis 2.86 0.52 0.07 2 Trichophoxus floridanus 2.86 0.52 0.07 2 3.33 1.63 0.36 7 Unidentified Gammaridea 5.71 1.58 0.07 9 6.67 1.09 0.07 8 Caprellidea Phtisica marina, 8.57 1.58 tr. 14 Total Amphipoda 25.71 7.89 0.48 215 20.00 4.35 0.58 99 Mysidacea Bowmaniella portoricensis 2.86 1.05 0.07 3 Unidentified Mysidacea 2.86 0.52 0.07 2 Total MYsidacea 5.71 1.58 0.14 10 Decapoda Natantia Leptochela papulata 11.43 7.37 2.59 114 Unidentified Natantia 5.71 1.58 3.54 29 3.33 0.54 tr. 2 Reptantia Macrura Callianassa atlantica 5.71 1.05 2.72 22 Panullrus sp. larvae 3.33 0.54 tr. 2 Ano r muun:a Alb 6.67 1.09 2.90 27 Euceramu:p;raelonaus 2.86 0.52 0.54 3 Paguridae 8.57 2.10 0.41 22 10.00 2.17 0.58 28 Pagurus sp. 20.00 8.42 1.91 207 20.00 8.15 2.03 204 P. carolinensis 14.21 3.16 1.50 67 23.33 3.80 1.23 118 P. hendersoni 2.86 0.52 tr. 2 3.33 0.54 0.07 2 .t. longicarpus 2.86 0.52 0.07 2 P. piercel 3.33 0.54 0.51 4 Z. piercei? 2.86 0.52 0.48 3 PYlopagurus discoidalis 2.86 0.52 0.07 2 Brachyura Hepatus epheliticus 6.67 1.09 5.37 43 HYRoconcha arcuata 5.71 1.05 0.14 7 3.33 0.54 1.09 5 Mithrax pleuracanthus 3.33 0.54 4.71 18 Parthenope sp. 3.33 0.54 2.18 9 Finnina sp. 2.86 0.52 0.07 2 Xanthidae 5.71 1.05 0.14 7 Unidentified Brachyura 22.86 4.21 8.79 297 13.33 2.17 1.31 46 Total Decapoda 54.29 33.16 22.96 3046 63.33 22.28 21.97 2803 Unidentified Crustacea 2.86 0.52 0.07 2 Sipunculida. Aspidosiphon spinalis 11.43 2.63 0.27 33 13.33 8.15 1.74 132 255 Table 7.4 (Continued) Winter 1980 Summer 1980 F N v IRI F N v IRI Unidentified Sipunculida 2.86 0.52 9.54 29 Tot. 1 Sipunculida 14.29 3.16 9.81 185 13.33 8.15 1.74 132 Ectoprocta 2.86 0.53 0.07 2 Diaperoecia floridana Echinodermata Asteroidea Astropecten sp. 3.33 0.54 2.18 9 A. articulatus 10.00 1.63 10.01 116 A. duplicatus 3.33 1.63 1.52 11 Total Asteroidea 16.67 3.80 13.71 292 Ophiuroidea Unidentified Ophiuroidea 28.57 5.26 1.16 183 23.33 3.80 4.86 202 Echinoidea Clypeasteroida 3.33 0.54 0.22 3 Holothuroidea Unidentified Holothuroidea 5.71 1.05 6.13 41 Chordata Ascidiacea Unidentified Ascidiacea 2.86 0.53 11.92 36 Pisces Decapterus punctatus 3.33 0.54 4.42 17 Unidentified fish scales 2.86 0.52 0.07 2 Unidentified Teleostei 17.14 3.16 5.18 143 3.33 0.54 1.31 6 Total Pisces 20.00 3.68 5.25 179 6.67 1.09 5.73 45 Number of stomachs examined so 43 Examined stomachs with food 35 30 19" I 256 Stenotomils acilleatus TAXON zu WINTER 1980 A AMPHIPODA 3982 8 POLYCHAETA 709 C CUMACEA 555 D CHAETOGNATHA 503 60- E DECOPODA 439 w A IF CEPHALOCHORDATA 247 G PISCES 222 40- H PELECYPODA 13 I SIPUNCULIDA I z 20- C E F G H 0- - 20- w 40- 0 > So- aoj so- SUMMER 1980 ZRZ H A 247 a 172 C 3 X 60- D 0 w E 294 CD 2 F 338 :3 40- G 282 z H 1057 1 213 20- 0- -A a C G w 220- D > 41 Li So % FREQUENCY ('0%) I I Figure 7.5. Frequency, number, volume (percents) and index of relative importance (IRI) of higher taxonomic groups of food in the diet of Stenotomus aculeatus. 257 Table 7.5. Percent frequency occurrence (F), percent number (N), percent volume M, and index of relative Importance (IRI) of food items in Stenotowus aculeatus stomachs for both sampling periods. tr trace volume. Taxon, Winter 1980 Summer 1980 Food Item F N V Iff F N V IRI Cnidaria Hydrozoa Unidentified Hydrozoa 2.94 0.11 0.21 1 2.56 0.12 0.27 1 Annelida Polychaeta Arabella iricolor 2.94 -0.11 3.20 10 Armandia maculata 8.82 0.55 0.64 11 Cirratulidae, 2.56 0.12 0.27 1 Eunicidae 2.56 0.12 2.66 7 Exogone sp. 2.56 0.12 0.27 1 Glycera sp. A 2.94 0.11 2.35 7 Lumbrineris, sp. 2.56 0.12 0.27 1 Maldanidae 2.94 0.11 1.49 5 Nereidae 2.56 0.12 0.27 1 Opheliidae 2.56 0.12 1.86 5 Phyllodocidae 2.94 0.11 0.43 2 Sabellaria vulgaris 2.94 0.11 0.21 1 Sthenelais boa 2.56 0.12 1.06 3 Unidentified Polychaeta 20.59 0.77 7.04 161 5.13 0.36 0.53 5 Total Polychaeta 41.18 1.88 15.35 709 20.51 1.19 7.18 172 Molluscs Gastropods Natica pusilla 5.13 0.24 0.27 3 Philine sagra 2.56 0.12 0.27 1 Unidentified Gastropods, 2.56 0.12 2.13 6 Total Gastropods 7.69 0.48 2.66 24 Pelecypoda Ervilia concentrica 12.82 73.36 9.04 1056 Pteria colymbus 2.94 0.11 0.21 1 Unidentified Pelecypoda 5.88 0.33 0.85 7 Total Pelecypoda 8.82 0.44 1.06 13 12.82 73.36 9.04 1057 Crustacea Ostracoda Ostracoda B 2.94 0.11 tr. <1 Ostracoda C 2.94 0.11 tr. <1 Total Ostracoda 5.88 0.22 tr. 1 Copepoda A,lteutha sp. 2.94 0.11 tr. <1 Bradya sp. 2.56 0.12 tr. <1 Calanoida 8.82 0.55 tr. 5 7.69 0.83 0.27 8 Harpacticoida 2.56 0.36 tr. I Labidocera aest1va 2.94 0.11 tr. <I Longipedia helgolandica 2.56 0.12 tr. <1 Temora turbinata 10.26 6.06 0.53 68 Total Copepoda 14.71 0.77 tr. 11 20.51 7.49 0.80 170 Branchiura Argulus sp. 2.56 0.12 tr. <1 Cumacea Cyclaspis varians 14.70 0.77 0.64 21 Oxyurostylis smithi 20.59 10.28 4.05 295 Unidentified Cumacea 8.82 0.77 0.64 12 7.69 0.36 tr. 3 Total Cumacea 32.35 11.82 5.33 555 7.69 0.36 tr. 3 Isopoda Erichsonella filiformis 2.94 0.11 0.64 2 1 Paracerceis caudata 2.94 0.11 0.43 2 Total Isopoda 2.94 0.22 1.07 4 258 Table 7.5 (Continued) Winter 1980 ummer 1980 Amphipoda - F N v Iff F N v IRI Gammaridea Ampeliqca sp. 2.56 0.12 0.27 1 A. agassizi 2.94 0.11 tr. <1 Amphipoda E 2.94 0.66 0.21 3 7.69 0.83 0.27 a Amphithoidae 2.94 0.11 0.21 1 Corophiidae 5.13 0.47 0.27 4 Erichthonius brasiliensis 17.65 19.56 9.81 518 Gitanopsis sp. 5.88 0.44 0.21 4 2.56 0.12 tr. @1 Maera sp. 2.94 0.11 0.21 1 Microdeutopus myersi 2.94 '0.22 tr. 1 2.56 0.12 0.27 1 Photis sp. 5.88 0.22 0.21 3 5.13 0.47 0.27 4 Z. pugnator 8.82 0.88 0.43 12 Podoceridae 2.94 0.33 0.21 2 odocerus sp. 14.70 5.64 2.56 120 Rudilemboides naglei 2.56 0.12 tr. <1 Stenothoe georgiana 20.59 2.43 0.64 63 Synchelidium americanum 2.56 0.12 tr. <1 Unidentified Ganmaridea 14.70 2.10 0.85 43 12.82 1.07 0.00 14 Caprellidea Caprella sp. 2.94 0.11 0.21 1 @j. penantis 5.88 0.22 0.43 4 2.56 0.71 0.27 3 Luconacia incerta 14.70 6.74 4.48 165 2.56 0.12 0.27 1 Phtisica marina 17.65 3.42 2.99 113 5.13 0.36 0.27 3 Caprellidae A 17.65 1.77 2.99 E4 Unidentified Caprellidea 17.65 1.77 1.71 61 Hyperiidea Lestrigonus sp. 2.56 0.12 tr. <1 Total Amphipoda 52.94 46.85 28.36 3982 35.90 4.76 2.13 247 Mysidacea Bowmaniella portoricensis 14.70 0.88 1.49 35 12.82 0.95 2.93 50 Promysis atlantica 5.88 0.44 0.64 6 Total Mysidacea 20.59 1.33 2.13 71 12.82 0.95 2.93 50 Decapoda Natantia Alpheidae 2.56 0.12 0.27 1 Hippolytidae Z.94 0.11 0.21 1 Latreutes parvulus 8.82 8.18 7.68 140 Lucifer faxoni 7.69 2.14 2.93 39 Palaemonidae, 2.94 0.11 0.21 1 Processa sp. 2.56 0.12 tr. <i Sicyonia typica 5.13 0.24 2.39 13 Synalpheus longicarpus 2.56 0.12 2.39 6 Unidentified Natantia 11.76 0.44 1.71 25 Reptantia Anomura Pagurus sp. 2.56 0.12 0.27 1 P. carolinensis 2.56 0.12 0.27 1 Brachyura Brachyura megalopae 2.56 0.24 0.27 1 Unidentified Brachyura 5.13 0.24 0.53 4 Total Decapoda 23.53 8.84 9.81 439 23.08 3.45 9.31 294 Sipunculida. Aspidosiphon misakiensis 2.56 0.12 0.27 1 A. spinalis 2.94 0.11 0.21 1 12.82 0.71 3.72 57 Uni-de-n-tl-fi-ed Sipunculida 2.94 0.11 tr. <1 15.38 0.83 2.66 54 Total Sipunculida 2.94 0.22 0.21 1 25.64 1.66 6.65 213 Ectoprocta Dia_peroecia florldana 2.94 0.22 0.21 1 2.56 0.12 tr. <1 Echinodermata Ophiuroidea 11.76 0.44 1.07 18 17.95 0.83 4.52 96 Chaetognatha Unidentified Chaetognatha 14.71 24.20 10.02 503 259 Table 7.5 (Continued) Winter 1980 Sumer 1980 F N v IRI F N v IRI Chordata Cephalochordata Branchlostoma caribaeum 14.70 1.66 15.14 247 7.69 4.28 39.63 338 Pisces Unidentified Teleostei 20.59 0.77 10.02 222 17.95 0.83 14.89 282 Number of stomachs examined 49 .47 Examined stomachs with food 34 39 260 Lutlanils campechanus so- WINTER 1980 TAXON IRI A A PISCES 7468 8 DECAPODA 673 w 40- C AMPHIPODA Gee go JE D OSTRACODA 167 M C E STOMATOPODA 0 z 20- GASTROPODA 0 D 0-- - - - - 20- Uj 40- 0 > So- So- 100 SUMMER 1980 IRI 60- A 44T4 - B 864 C 209 LLJ 40- A D 0 E 621 F 158 Z 20- F 0 0-- - - - - - - - 20- 40- 0 > Go- so- 100-A % FREQUENCY( L Figure 7.6. Frequency, number, volume (percents) and index of relative importance (IRI) of higher taxonomic groups of food in the diet of Lutjanus campechanus. 261 Table 7.6. Percent frequency occurrence (F), percent number (N), percent volume (V), and index of relative importance mr) of food items in Lutlanus campechanus stomachs for both sampling periods. tr trace volume. Taxon Winter 1980 Summer 1980 Food Item F N V IRI F N V IRI Mollusca Gastropods Cavolinia longirostris 12.50 12.50 0.21 159 Crustacea Ostracoda Ostracoda A 16.67 j0.00 0.01 167 Stomatopoda Squilla sp. 12.50 4.17 45.53 621 Cumacea Cyclaspis varians 12.50 4.17 0.04 53 Isopoda Serolis mgrayi 12.50 4.17 tr. 52 Amphipoda Erichthonius brasiliensis 16.67 10.00 0.01 167 12.50 16.67 0.04 209 Hippomedon sp. 16.67 10.00 0.01 167 Total Amphipoda, 33.33 20.00 0.02 668 12.50 16.67 0.04 209 Decapoda Natantia 0.01 Leptochela sp. 16.67 10.00 167 Thor sp. 12.50 4.17 0.79 62 Unidentified Natantia 12.50 4.17 0.25 55 Reptantia Macrura _Scyllarus chacei 12.50 4.17 0.62 60 Brachyura Ovalipes stephensoni 16.67 10.00 0.18 170 Portunus anceps 12.50 4.17 0.46 58 Unidentified Brachyura 12.50 4.17 0.08 53 Total Decapoda 1 33.33 20.00 0.19 673 37.50 20.83 2.20 264 Chordate Pisces Decapterus punctatus 12.50 20.83 37.28 726 Haemulon aurolineatum 12.50 4.17 5.39 119 Rhomboplites aurorubens 12.50 4.17 4.56 109 Stenotomus sp. 16.67 10.00 71.21 1353 Unidentified Teleostei 50.00 40.00 28.56 1952 25.00 8.33 4.76 327 Total Pisces 50.00 50.00 99-77 7488 50.00 37.50 51.99 4474 Total stomachs examined 20 11 Examined stomachs with food 6 8 262 Table 7.7. Percent frequency occurrence (F), percent number (N), percent volume M, and index of relative importance (IRI) of food items in Mycteroperca microlepis stomachs for both sampling periods. Winter 1980 Sumer 1980 Food It+ P N V IRI F N V IRI )OIollusca Gastropods Natics canrena 50.00 16.67 3.15 991 Crustacea Decapoda Ranilia muricata 50.00 33.33 13.01 2317 Ohordata Pisces Rhomboplites aurorubens 50.00 50.00 99.82 7491 Unidentified Teleostei 50.00 50.00 0.18 2509 100.00 50.00 83.84 13384 Total Pisces 100.00 100.00 100.00 20000 100.00 50.00 83.84 13384 Total number of stomachs examined 2 3 Examin ed stomachs with food 2 2 263 Overlap in Diet: Results of cluster analysis (Figure 7.7) indicated very low similarity in diet among predator species examined in both winter and summer. Individual similarity comparisons between species (Figure 7.8) were also low. In winter, 1. pagrus and C. leucosteus were most similar in diet. Although the most abundant prey species for these two predators differed, they shared many of their less abundant prey species. Rhomboplites aurorubens and S. aculeatus both had Oxyurostylis smithi as an abundant prey species and were more similar in diet to each other than to any other predator group. Centropristis striata was joined to these two predators because it primarily consumed Erichthonius brasiliensis, the second most abundant prey species in the diet of S. aculeatus. Mycteroperca microlepis and L. campechanus both consumed fish and were joined together at a low similarity value. In summer, S. aculeatus and R. aurorubens were the two species most similar in diet, although similarity values were again quite low. Pelecypods (Ervilia concentrica), copepods (Temora turbinata), and pelagic decapods (Lucifer faxoni) were common in the diet of both species. Centropristis striata and Calamus leucosteus overlapped in diet slightly. Although the most abundant prey consumed by these two species differed, they had some prey in common which were not consumed as much by other species (e.g. pagurids, ophiuroids). In summer, L. campechanus consumed many more invertebrates (Table 7.6) and was more similar in diet to P. pagrus, which also included more fish as well as invertebrates in its di7e-t. 'Mycteroperca microlepis remained primarily piscivorous and was grouped with these two species. Habitat of Prey Items: All predators examined fed on live bottom organisms to some extent, and some species appeared to be highly dependent on live bottom prey (Figure 7.9). Centropristis striata and P.'pagrus, in particular, consumed a large volume of live bottom species. @-t-enotomus aculeatus had a diet dominated by live bottom species in winter, but in summer this species consumed predominantly sand bottom fauna. Rhomboplites aurorubens fed mainly in the water coltimm. The large predators, M. microlepis and L. campechanus, consumed mainly fish from several habitats. DISCUSSION Randall (1967), in an extensive study of the food habits of 212 species of West Indies fishes, classified reef fishes into seven feeding types: (1) plant and detritus feeders, (2) zooplankton feeders, (3)sessile animal feeders, (4) "shelled" - invertebrate feeders, (5) generalized carnivores on a variety of mobile benthic animals, (6) ectoparasite feeders, and (7) fish feeders. Although most tropical reef fishes fit into more than one category and may even change from one type to another with age, 1@andall grouped his 212 species into one of these categories based on the volume of major prey taxa. Most fishes examined in the present study were generalized carnivores on a variety of mobile benthic invertebrates and fish. This category included 264 SIMILARITY .8 .6 .4 .2 0 -.2 -.4 POgrUS POgrUS CO/Omms leucosteus Rhomboplites ourorubens stenotomus Oculeatus Centropristis striato mycteroperca microlopis Lutjonu Campechoflus WINTER Rhomboplites ourorubens stenotomus Ocalootus Centropristis striato CO/Omas laucostaus Pagrus Pagru Lutionu Compechanus h mycteroperea microlep -A SIMILARITY SUMMER Figure, 7.7. Dendrograms depicting overlap in diet among predators. 265 A t.4 f3 lb IQ6 centropristis . striato 03 /fuca/amus .05 .06 Apst'pus .05 .11 1.29 Pagrus 1.01'anils 00 .01 05 .06 . . . . . . . . . . . -mycferoperco microlopis *00 .00 .01 .01 .17 stenotomas .20 .22 .081-12 .01 JDO leatus I I --I- @@j WINTER 0 >.?-O E] 2.10 to. % < .10 Z z 14, t a Q t. zi I. . . . . . . . . . . . . centropristis Rhomboplite 17 Ourorabs'"s CO/Omus .16 .05 loucosteus Pagrus Pagrus -16 1.10 1.12 Lufjonu compecoanus .021-04 .14 mycteroperca microlep .03 .02 .02 .08 .13 stenotom .09 .21 .05 .05 .01 'o, N aculeatus SUMMER @O6 .290 Figure 7.8. Diet overlap between predators as measured by the Bray-Curtis similarity measure. 266 HABITAT OF PREY ITEMS 100- 80- WINTER W 60- :E 0 40 20 0 0 L16 0 100- 0 SUMMER z UJ 60 cc W 40 CL 20 0 z 0 Live bottom spp. 13 Sand spp. 0 Wiater column spp. 0 Unknown spp. Figure 7.9. Percent of total volume of food consisting of live bottom organisms, sand bottom organisms, water column organisms or prey for which habitat is unknown. 267 the black sea bass, C. striata. Link (1980) studied the food habits of C. striata and also noted a generalized diet. Many of the prey (decapods, fishes) that were frequently consumed were also frequent in the present study. The most noteworthy differences were the relatively high frequency of gastropods and the infrequency of amphipods in stomachs which he examined. The most noteworthy seasonal difference in the food habits of black sea bass im the present study was the relative abundance of amphipods in the diet in winter and their scarcity in the diet in summer. Decapods were the most abundant prey taxon in summer and this was also found to be true for black sea bass collected off North Carolina (Volume II). Red porgy, P. pagrus, was also a generalized predator on mobile benthic species. Manooch (1977) noted a very diverse diet in this species and found decapods and fish were frequent food items, a finding duplicated by the present study. Manooch (1977) also noted a high frequency of mollusks in winter (24.0%)and summer (30.9%). Mollusks were very infrequent in the diet of red porgy in the present study; polychaetes and amphipods, which Manooch found to be rare, were frequently consumed. Because Manooch (1977) included intestine contents in his analysis, shelled mollusks, which are slowly digested and may be retained in the intestine, would appear to be more frequent than more rapidly digested polychaetes and small crustaceans. Southern porgy, S. aculeatus, was also a generalized benthic carnivore, and is apparently a very opportunistic predator as evidenced by the large seasonal differences in diet (Figure 7.5). Southern porgy switched from a diet dominated by amphipods in winter to a diet dominated by bivalves, which were abundant following recent settlement from the plankton, in summer. Southern porgy collected off North Carolina had a diet dominated volumetrically by algae, reflecting the increased availability of algae for food in North Carolina waters (Volume II). Southern porgy apparently change their diet depending on prey availability, and opportunistically feed on whatever prey is abundant. These generalized carnivores,such as black sea bass, red porgy, and southern porgy, include the greatest number of species of any feeding type on tropical reefs (Randall 1967, Parrish and Zimmerman 1977) and are also represented by many species on live bottom reefs in the South Atlantic Bight. Other dominant species which are included in this feeding type are Haemulon aurolineatum, Equetus lanceolatus, Bothus ocellatus, Scorpaena spp., and Dactylopterus volitans (Randall 1967). Some of the most abundant live bottom species (S. aculeatus and H. aurolineatum) are included in this group. These species fed heavily on organisms from sand bottom areas of the shelf. Haemulon aurolineatum is known to move off the reef to feed over sand bottom at night, returning to the reef during the day (Parrish and Zimmerman 1977). This feeding behavior may also occur in other species which fed heavily on sand bottom organisms (e.g., C. leucosteus, S. aculeatus) and could function in transferring energy from sand bottom areas to adjacent live bottom. Two species analyzed in the present study were fish feeders: MycteroperSa microlepis and Lutjanus campechanus. Both species fed on other live bottom or schooling pelagic fishes. Lutjanus campechanus also frequently consumed invertebrates, as noted by @i-radley and Bryan (1975). Other species collected in the present study and categorized as piscivores (Randall 1967)"were Gingly- mostoma cirratum, Rhizoprionodon terraenovae, Synodus spp., Rachycentron canadum, Caranx spp., and Seriola dumerili. Most of these species were present but uncommon at our study sites. 268 Rhomboplites aurorubens examined in the present study was a zooplankton feeder which also fed heavily on benthic invertebrates. Grimes (1979) examined the food habits and morphology of this species and also concluded that this species was a water column forager. Grimes (1979) examined stomachs of 'R. aurorubens caught off the Carolinas and, although @e examined few stomachs from winter (N = 2), his summer results (N = 46) were quite different than those presented here. Cephalopods, pelagic gastropods, colonial tunicates, and hyperiid amphipods dominated volumetri- cally whereas fish, a dominant item in the present study, constituted a small volume of the diet. The different results between these two studies and the seasonal variation found within both studies is not surprising in light of the planktonic diet of this species and the marked seasonal fluctuations in species composition of plankton communities in the South Atlantic Bight (Bowman 1971). Other abundant live bottom species caught in the present study and which feed in the water column include Decapteru punctatus-and Apogon 2seudomaculatus (Randall 1967). Calamus leucosteus, which was very generalized in its food habits and could be included in several feeding categories, also fed heavily on shelled invertebrates (mollusks, barnacles, hermit crabs). Randall included several related species of Calamus in this feeding type, Other species found on live bottom in the present study and which Randall included in this group were Eaemulon plumieri and Sphoeroides spengleri. k1though attached sessile form; (@ntho`zoans, hydroids, bryozoans, ascidians, sponges, etc.) were included in the diet of most predators, no predator specialized on these animals. This is not surprising since these organisms often possess chemical or mechanical defenses which deter many preda- tors (Randall 1967, Stoecker 1980). Many of the mobile benthic invertebrates that were important as prey are associated with sessile forms (e.g., alpheid shrimps, caprellids), and these sessile forms may have been accidentally ingested by fish preying on mobile species, Of the 11 fish species noted by Randall. as sessile animal feeders, only Acanthostracion quadricornis commonly occurs in the South Atlantic Bight and was caught at all inner and middle shelf stations. No ectoparasite feeders were found among the species examined. Grimes (19 79) noted a high incidence of fish scales in Rhomboplites aurorubens stomachs and attributed this to scale eating or parasite picking. However, Randall. (1967) noted fish scales in the stomachs of several species and concluded that they were probably eaten after they were detached from schooling pelagic fishes as a result of the activity of other predators. Rhomboplites aurorubens is primarily a plankton feeder and could ingest scales in this manner. No ectoparasites were found in stomachs by Grimes (1979) or in the present study. The only known ectoparasite feeder (Randall 1967, Cressy and Lachner 1970) captured in the present study was Echeneis naucrates. None of the species included in the present analysis were plant and detritus feeders; however, Aluterus schoepfi, a common shelf and live bottom species which was captured in this study, feeds on plant material (Randall 1967). Overlap in diet among the fishes examined was low compared to similarity values found in other studies (McEachran et al. 1976, Ross 1977, Sedberry 1980). Most comparisons between species in this study resulted in values 269 less than 0.20, and groups of predators were joined together at even lower similarity levels, usually less than zero. Sedberry (1980), using the same clustering algorithm on dominant shelf fishes in the Middle Atlantic Bight, found interspecific comparisons as high as 0.68, with most predator groups formed at levels higher than 0.20. Whereas, Sedberry (1980) found most benthic feeding fish shared abundant prey species (mainly two epifaunal amphipod species), the present study indicates that the live bottom fish community is supported by a variety of organisms, with no species that were important to several predators. The higher diversity of fishes on live bottom in the South Atlantic Bight (see Chapter 6 for further discussion) should result in finer resource partitioning (Huston 1979), and thus result in lower food overlap. The complex habitat structure of live bottoms provides abundant epifaunal, infaunal, and water column food resources. Adjacent sand bottom areas protected from erosion by surrounding rock and the sand layer often noted on rock surfaces (Chapter 3) provides feeding ground for infaunal feeders. The variety of food resources allows more specialization among predators and less overlap in diet. These alternative food sources for the live bottom fishes examined in this study and their relative importance are depicted in Figure 7.10, which illustrates the basic trophic structure observed at our live bottom study areas. Predation can be an important factor 'in controlling community structure of infaunal (Virnstein 1977, 1979) and epifaunal (Paine 1974, Peterson 1979)' communities, and grazing by herbivores influences community structure in algal communities (Lubchenco 1978). Predation and grazing by fishes may influence the structure of live bottom communities; however, investigation of these effects was beyond the scope of this study. Because natural phenomena such as predation may affect live bottom community structure as much as petroleum development could, the importance of predation as a factor in community structure should be investigated in future studies. Such studies should include predator removal, exclosure, and enclosure experiments. IMPACT/ENHANCEMENT The potential impact of oil and gas development on live bottom fishes may be directly related to their food habits and the trophic structure of live bottom areas. Drilling itself would destroy potential prey habitat. Overboard discharge of drill cuttings and drilling muds may cause smothering of benthic organisms resulting in reduced prey abundance. Introduction of toxic concentrations of trace metals and hydrocarbons could also reduce prey abundance in localized areas which would, in turn, result in localized reduction of predator abundance. Fishes are highly mobile and may be able to avoid areas disturbed by oil development. However, many reef fishes, including the priority species L. campechanus and R. aurorubens.(Fable 1980) may move very little from a "home" reef. In addition, many species feed heavily on live bottom organisms. Destruction of a live bottom habitat would adversely affect those species that could not utilize infaunal sand bottom prey or could not be accommodated on an adjacent reef because of space limitations thought, by some, to control reef fish population size (Smith and Tyler 1972, Luckhurst and Luckhurst 1978). Besides eliminating food resources, oil development has other potential effects on the feeding of fishes. A major effect of petroleum on marine 270 M.MICROLEPIS L.CAMP CHANUS C.STRIATA P. PAGRUS R.AURORUBENS C. LEUCOSTEUS S. ACULEATUS PLANKTIVOROUS FISH'S BENTHIC DING FISO IN FAUNA IMainly sand bottom species 2Mainly mobile forms associated with attached fauna 30ther abundant demersal species (H. aurolineatum, E. lanceolatus) 4Schooling pela-gic species (D. punctatus, clupeids, anchovies) Figure 7.10. Schematic food web depicting alternate food sources for live bottom fishes. Wider lines indicate major food sources; narrower lines indicate l2ss important food sources. 271 organisms is a reduction in chemosensory ability (Kittredge 1974). Feeding in fishes is often initiated through chemoreception (Kleerekoper 1969, Hara 1971), and chemosensory cues have been shown to be important in the feeding behavior of several fishes (Bardach and Case 1965, de Groot 1969). Oil spills could negatively affect these species. Reduced visibility caused by drilling could also decrease fishes' ability to locate prey visually. I On the other hand, drilling and production structures offer a potential for enhancement of food resources. These platforms would provide additional substrate for the growth and production of sessile invertebrates and associ- ated mobile species which are important prey for many fishes. Drilling and production structures would also attract schooling pelagic species (Klima and Wickham 1971) which are important prey for top carnivores, including priority species of commercial and recreational importance. CONCLUSIONS -Seven fish species were proposed as priority species for food habits analysis: Centropristis striata, Epinephelus niveatus, Lutjanus campe- chanus, Mycteroperca microlepis, M. phenax, Pagrus pagrus, and Rhomboplites aurorubens. Epinephelus niveatus and M. phenax were not collected, and two dominant non-priority species were substituted: Stenotomus aculeatus and Calamus leucosteus. - Black sea bass, Centropristis striata, and red porgy, Pagrus pagrus, were generalized carnivores which fed mainly on live bottom taxa. Both of these species fed heavily on decapods and fishes; however, black sea bass also consumed many amphipods, whereas red porgy fed heavily on polychaetes. -Vermilion snapper, Rhomboplites aurorubens, is a zooplankton feeder which fed primarily in the water column. Food habits of vermilion snapper varied greatly with season; cumaceans, ostracods, and amphipods were the most important prey in winter, whereas fish, decapods, and copepods were most important in summer. -Whitebone porgy, Calamus leucosteus, fed primarily on sand bottom taxa, but many live bottom taxa were also consumed. Decapods, polychaetes, and gastropods were the most important prey during both seasons. -Southern porgy, Stenotomus aculeatus, is a generalized carnivore which consumed many live and sand bottom species. Amphipods, fishes, and poly- chaetes were the most important prey in winter, whereas fishes, pelecypods, and amphipods were the most important prey in summer. -Red snapper, Lutjanus campechanus and gag, Mycteroperca microlepis, both fed heavily on fishes. Red snapper also consumed several invertebrates from sand and live bottom habitats. -Overlap in diet among predators was low. This is probably due to the high diversity of predator and prey communities, and to the various alternative food sources (infauna, epifauna, zooplankton) found in live bottom areas. 272 The impact of oil development on live bottom fishes may be directly related to their food habits and feeding behavior. Drilling itself and mud disposal could cause destruction of prey habitat or smothering of prey organisms. Petroleum from oil spills may reduce prey abundance or inter- fere with prdy detection and feeding behavior in fishes. Drilling andjoproduction platforms may enhance fish productivity by providing additional substrate for epifaunal invertebrates, which are an important food source for some priority species. Attraction of schooling pelagic fishes to production structures could provide additional food for top carnivores (snappers and groupers). 273 CHAPTER 8 METHODOLOGY EVALUATION AND RECOMMENDATIONS FOR FUTURE STUDIES METHODOLOGY EVALUATION Overall, the wide variety of sampling gears utilized in this study provided a good characterization of the diverse fauna present at the study sites. Due m o constraints in funding and the amount of time available to analyze samples, the number of replicate collections obtained using each gear was limited. Thus, any species were probably missed, especially cryptic forms common under ledges and in crevices. Additionally, estimates of the relative abundance and frequency of occurrence of species collected were crude due to high variability among replicates (as noted below). Even so, this study provides a far more comprehensive data base on live bottom biota than any previous studies in the South Atlantic Bight. Evaluations of each gear are provided below. Remote Censusing Gears: Television Transects - Reconnai ssance transects performed using the underwater television system were extremely useful in defining the extent of live bottom, even when this type of bottom was not detected on the fathometer. The camera was also very useful in assessing: (1) the percentages of various bottom types within the study area; and (2) the presence and relative frequency of megafauna and large fish which were often not captured in removal sampling gears. A limitation of this gear is the relatively narrow field of view, but our technique of analyzing the tapes does provide an estimate for the surround- ing area. Better quantitative estimates of selected invertebrates could have been obtained if the camera had been mounted on a sled and towed in transects across the study areas so that the sled was in continuous contact with the bottom. This would eliminate variability in the width of the sled paths analyzed and permit accurate counts instead of presence/absence frequency estimates. However, using a sled at many of the sites might have resulted in camera damage or loss from rock relief. Color video would have greatly improved our ability to identify organisms, although these cameras are substantially more expensive. Still Camera Transects - Remote still photographic transects conducted 3 m above bottom helped to confirm television observations and provided a more quantitative means of establishing densities of selected fauna. Unfortunately, poor water clarity and the limited number of live bottom photographs analyzed decreased the effectiveness of this technique. When water clarity permits a good view of the bottom from this height, this technique should prove quite effective, provided that a large number of quadrats are assessed. The photo- graphs taken 1 m above bottom were not as useful as we originally thought they would be, and we do not recommend this effort in future studies * From 1 m above bottom, the size of the quadrat analyzed is small (0.5 m2), and recog- nizable fauna is not well represented due to patchy distribution patterns. Removal Sampling Gears: Trawl - The trawl used in our study was the most effective gear for sampling a high diversity of demersal fishes. Because the distance towed was known, we were able to obtain standardized (by area) estimates of fish abun- dance and biomass. The trawl was less effective at capturing large, highly 274 mobile species, and probably missed many small cryptic forms as well. Because of diel changes in the fish fauna, replicated tows are necessary for both day and night. Although it is not a quantitative sampler for invertebrates, the trawl did catch large sessile species (sponges, octocorals) and several mobile decapod crustaceans that were missed with other gears. , Baited Fishing Gears - Although the baited gears were not as effective at capturing fishes present at our study areas, these gears were the only way to catch fish at untrawlable sites. Vertical longlines were the least effec- tive gear and should not be deployed in future studies. Hook and line collections were useful, but more time should be spent on this effort. Electric reels and fishing rods are easier to deploy than manual snapper reels and should be substituted in hook and line collections. Traps were effective in catching some fish species at stations which could not be trawled. They were particularly useful at outer shelf stations where water depth and high drift speed made hook and line fishing difficult. Fish Sled - As stated in the original proposal, a question of significance to this study concerns the importance of live bottom areas as nursery habitats for larval and juvenile fishes. Conventionally, larval fishes are collected with plankton nets that sample at the surface or throughout the entire water column. As a result, larvae associated with the bottom are not frequently sampled. Most juvenile fishes (particularly young-of-the-year) are probably also undersampled because of their ability to avoid sampling gears designed to capture larvae and adults, and because most conventional surveys do not employ gear specifically designed to catch small fishes (20 - 100 mm). The epibenthic sled used in this study provided a means of quantitatively sampling larval fishes that occur within I m of the bottom. The opening and closing mechanism, when properly functioning, insures that the net is collecting only when the gear is in contact with the bottom, thus preventing contamination of the sample by non-resident water column plankton. Mouth opening, mesh size and towing speed are adequate for sampling fish larvae; however, this gear is apparently not an efficient sampler of juvenile fishes. Although specimens ranged in size from 2 to 78 mm SL, mean minimum and maximum lengths were 9.1 mm and 11.1 mm, respectively. Full fin ray complements are frequently present in larvae at sizes of 9 - 11 mm, but pigmentary and behavioral changes associated with transition to the juvenile stage generally occur at larger sizes (15 - 20 mm or larger). Well over 90% of the specimens collected with the epibenthic sled were clearly larval or postlarval in form and pigmentation. Of the juveniles collected, the majority represented groups that are characteristically sedentary or slow moving sucb as ophichthid eels, ophidiids, triglids, carapids, gobiids, blenniids, batrachoidids, and dactyloscopids. Although juveniles of some active swimming groups (e.g. two apogonids and one pomacentrid) were taken, they were, for the most part, notably absent from the samples, apparently due to their ability to avoid the small, relatively slow moving, fine mesh net. Juveniles of the seven priority species are not sedentary and, thus, not likely to be taken in the epibenthic sled. The importance of live bottom areas as nursery grounds for these species and m4ny others cannot be determined using gear that samples primarily larval and postlarval stages. Although some larvae may become associated with the bottom at small sizes, well before juvenile transition, other (e.g. groupers) remain planktonic to sizes of 15 mm 275 or more, at which time they settle and undergo morphological and behavioral changes related to juvenile transition. In these late settling species, bottom residence commences at sizes that are already beyond the typical sampling capability of the sled. Additional methodological problems associated with the sled involved gear malfunction and sampling design. During the winter cruise, the opening and closing devicewas not functioning properly, and the net was at least occas- sionally open through the water column during setting and retrieval. Unfortunately, there is no way to determine how often and in which collections this occurred. The uncertainty of the opening and closing operation was alleviated during the summer cruise by locking the net open. Thus, a portion of each sample consists of specimens collected in the water column. If several tows had been made in a simple oblique pattern (without allowing the net to fish at the bottom), some rough indication of the magnitude and composition of a water column sample would be available. WithoVt these "controls", we can only assume that each sample represents primarily bottom associated specimens. Finally, with the present sampling design it is difficult to draw sound conclusions concerning the preferential association of the species collected in relation to live bottom habitat. Plankton nets are rarely towed on the bottom in larval fish surveys, and consequently, we know very little about the distribution and habits of epibenthic fish larvae. Some species may well be restricted to live bottom while others may be randomly distributed over the bottom. The marked influence of Gulf Stream intrusion on diversity at OS02 ustrates the overriding importance of currents and water masses to larval fish distribution. Recognition of true resident species can only be achieved ill if additional comparative tows are made on sand bottom areas. This was not, however, included in the scope of this study. Dredges - Both the rock dredge and the Cerame-Vivas dredge were quite effective in collecting sessile and encrusting macrofauna including cnidarians, ascidians, bryozoans, small sponges, and octocorals. Since the gears were equipped with large mesh bags, smaller motile faunal components (such as amphipods and polychaetes) were not effectively sampled, because most were undoubtedly washed out of the bags. As noted previously, only two replicate tows were made at all study areas. A greater number of tows could not have been analyzed in the time allotted in the contract without sacrificing sample workup from other gears. Due to the high variability noted in replicated dredge catches, more tows at every station would have provided a better assess- ment of community structure. Suction Sampler and Smith-McIntyre Grab - Sampling small invertebrates with the suction sampler proved to be a very simple, yet effective, technique. Samples were quantitative because suctioning was confined to the surface area within the walled box placed on the substratum. The Smith-McIntyre grab, which was substituted for the suction sampler at deeper stations, was less reliably quantitative because the volume of sediment sampled was not consistent for all collections, especially when the grab hit hard bottom without a sand veneer. However, we know of no other remote quantitative sampler which would, have been more effective on hard surfaces. An additional problem with grab sampling is that our assessment of the exact bottom type sampled is necessarily conjectural and based solely on the contents of the grab. This problem could be rectified by deploying a still camera with the grab as done by Boesch et al. 276 (1977), but the cost would be substantially increased. With respect to quantitative population estimates, we found suction and grab catches to be highly variable between replicates. We attribute this variability primarily to natural dispersion of the organisms and bottom substratum variability. Differences in sampling efficiency may also have been a factor. An examination of distributional patterns for the ten dominant sppcies revealed that most were highly contagious. Information on the effec- tive level of replication needed to detect significant changes in population density of these species was calculated by the expression: 2 s n = - 1 2 D2sE2 where s is the variance, R is the arithmetic mean and D is expressed as S3j (or the standard error of the mean) (Elliott 1977). As shown in Table 8.1, the level of replication necessary to detect (with 95% confidence) an estimate of the population mean, within + 40% of the true value, varied greatly among species. In most instances, the necessary number of replicates was much greater than five. Species accumulation curves (Figure 8.1) further point out the inadequacy of five replicates in censusing populations of patchily distributed organisms. Considering the large number of replicates needed to accurately assess the abundance of highly contagious organisms, we feel that our current efforts must suffice to keep survey costs minimal. In any case, suction and grab samplers at least provide crude abundance estimates of the smaller fauna not represented in trawl and dredge collections. Diver Assessments and Swimming Transects - Diver assessment allowed direct measurements of relief at inner and middle shelf study sites, but rock samples were difficult to obtain. Ledge faces and evident outcrops were typically sampled by divers, and most rock collections gathered by this method were somewhat eroded and biologically excavated by marine borers. Swimming transects aimed at delineating ichthyological assemblages were somewhat adversely affected by poor water clarity and other factors (i.e., species attraction, avoidance), but generally appeared to provide meaningful estimates. Stone et al. (1979) demonstrated that such diver transect counts can adequately approximate reef fish abundances, as well as determine the presence of cryptic fish species. Additionally, divers were able to detect the presence of certain large species not captured by trawl. RECOMMENDATIONS FOR FUTURE RESEARCH The scope of the first year study effort provided only limited information on seasonal changes in community structure. Furthermore, no study areas were located between Charleston, S. C. and Cape Fear, N. C. Our recommendations to sample live bottom areas during all four seasons and to relocate some stations to areas off South Carolina have already been incorporated into a second year study effort. These modifications should greatly assist in providing predictive information on live bottom community composition and structure in the South Atlantic Bight. Other recommended research, which would be especially valuable with respect to impact assessment, includes recolonization and growth rate studies on live bottom fauna. If these areas are adversely affected, there is no existing data base on which to predict expected recovery rates, particularly for the large invertebrate fauna. Additional information is also needed on Table 8alz index of dispersion (1, Elliott 1977) and estimated number of samples (n) needed to obtain an estimate of the population mean within � 402 of the* true value for the ten numerically dominant Invertebrate species in auction and grab samples. Asterisk Indicates significant deviation of I from Poisson distribution. Additional Information on each species is provided in Chapter ISOI IS02 IS03 MSOI HS02 MS03 OSOI OS02 OS03 n n I n I n I it I n I n WINTER Filograna implexa 24.0* 125 1.0 125 4707.1* 98 4.0* 125 Phyllochaetopterus socialis 26.8k 93 1.0 125 - - - - - - Splophanes bombyx 4.9* 14 2.1 66 0.5 21 1.8 38 4.0* 13 2.4 27 11.5* 36 3.9* 82 2.8* 16 Exogone dispar 9.1* 23 10.06 7.2* 3 5.2* 20 2.9* 14 2.0 125 - - - - - - Photis op. 3.0* 6 13.0* 10 5.0* 8 2.4 7 12-0* 8 13.7* 41 1.5 47 1.0 125 0.8 47 Podocerus op. 14.9* 6 46.9* 68 4.0* 8 3.9* 10 3-8* 63 0.9 23 1.4 30 3.0* 125 3.0* 125 Luconacia Incerta 26.9* 30 9.9* 12 1.2 5 11.9* 10 19.3* 30 1.4 30 1.3 56 2.0 125 2.0 36 Syllis spongicola 0.7 47 9.9* 52 2.4 12 11.7* 32 - - 27.0* 99 1.0 125 - - 2.0 50 Erichthonius op. A - - - - - - - - - - - - 6.6* 41 - - 5.8* 91 Ophlothrix anitulata 1.0 21 9.1*13 13.2* 8 9.5* 33 2.0 100 2.2 28 - - - - 1.0 125 SUMER Filograne Implexa 5.0* 125 3938.0* 125 41.0k 125 1973.9* 116 - - 75.7* 29 - - - - 3317.5* 113 Phyllochaetopterus socialls - - - - 1.0 125 4.0* 56 1.0 125 1.0 125 2.0 36 - - 2208.0* 125 Spiophanes bombyx 0.7 47 1.0 125 0.9 27 0.5 21 - - 1.0 125 57.8* 18 12.1* 9 4.8* 67 Exogone dispar - - - - 10.1* 25 0.9 27 1.0 125 - - - - - - - - Photis op. - - - - 13.8* 47 - - - - - - 6.3* 22 9.9* 62 1.3 56 Podocerus op. - - - - 2.0 125 0.7 47 6.0* 125 1.0 125 - - 1.0 125 5.1* 58 Luconacia Incerta -- - - - 11.6* 42 0.9 27 1.3 56 1.3 56 - - - - 7.7* 64 Syllis spongicola 12.0 125 3.0* 75 2.7 42 41.1* 25 9.0* 125 9.3* 20 - - 60.0* 125 2.2 47 Erichthontu; op. A - - - - - - - - - - - - 4.2* 31 2.0 36 315.5* 90 Ophi;3thrix angulata 2.4 27 21.8* 42 5.0* 125 - - 4.0 17 1.0 125 - - 1.0 125 U) 260- WINTER 1980 W 0 W a. (0 ISO- .01 W:.e 0 - , -, @r- - I '@ -, A z 140- W - -ISOI > 100- - - - ZS02 f IS03 M901 MS02 0901 i so - MS03 OS02 --OS03 20- A. 'V 5;0 106 156 2@00 256 @00 500 1060 te6 2000 606 656 116, 2010 1 3LO 1 Zo 1 5@* 1 6 W, CUMULATIVE NO. OF INDIVIDUALS U) 260- 00 W SUMMER 1980 0220- W U) 100- J d, Pt 140- W - > 100- -ISOI --IS02 J Go- ---1S03 MS01 D MS02 -0S01 I - - -MS03 --OS02 D 20- - - - OS03 -N-T-N-r-T@ 5;0 106 156 20100 25100 30100 35FOO 4000 4500 5;0 106 15'00 K6 060 3000 3500 0 lc@o 4000 4500 TOOO MW 6000 CUMULATIVE NO. OF INDIVIDUALS Figure 8.1. Species accumulation curves for invertebrates at stations sampled by suction and grab during winter and summer, 1980. r 4"* So I MS02 MS03 M A -MS01 MS02 _MS03 279 the diets of several of the dominant priority and non-priority fishes. While the current study is examining the diets of some species, constraints on the time allotted for laboratory analysis limited the number of stomachs which could be examined. Thus, food habits for different size (age) fish could not be considered, and more stomachs need to be examined for each species in general. This effort would not necessarily require further sampling since we are currently collecting more fish stomachs than we are able to analyze. Finally, if dr:ftling or production platforms are placed in the South Atlantic Bight near live bottom areas, we strongly recommend monitoring studies to assess whether effects from these rigs are negative, positive, or non-existent. 280 ACKNOWLEDGEMENTS South Carolina Marine Resources Research Institute and Georgia Coastal Resources Division personnel who contributed to this study as project personnel are listed in Tables 9. 1 and 9. 2, respectively, along with their areas of responsibility. Other people not designated as project personnel also contributed to the study effort. They include the crews of the R/V Anna, R/V Bagby, and R/V Dolphin to whom we express our gratitude. Special thanks are also expressed to Karen Swanson and Josie Williams for drafting the figures in this volume, to Mary Anne Carson who assisted in typing, and to Priscilla Hinde for her editorial effort. Additionally, appreciation is extended to the following scientists for their assistance in identification and verification of specimens. F. M. Bayer U. S. National Museum E. L. Bousfield Museum of Natural Sciences, National Museum of Canada W. Hartman Yale Peabody Museum G. Hechtel State University of New York T. Hopkins Dauphin Island Marine Laboratory C. Messing U. S. National Museum D. Mook Harbor Branch Foundation H. Porter University of North Carolina H. Ruetzler U. S. National Museum J. Thomas Newfound Harbor Marine Institute V. Zullo University of North Carolina 281 Table 9.1. Project personnel from South Carolina Marine Resources Research Institute and their areas of responsibility. NAME AREA OF RESPONSIBILITY Barans, C. A. Fish community analysis (review) Burrell, V. G. Jr. Project Leader, project management Calder, D. R. Invertebrate identification Clise, M. J. Technical support Gash, A. G. Data processing coordination Hodges, L. H. Secretarial support Hodges, W. T., Jr. Technical support Johnson, G. D.* Larval, juvenile fish identification and analysis Knott, D. M.* Invertebrate identification, community analysis; physical habitat description Maclin, M. S. Technical support Manzi, J. J. Algal identification Mathews, T. D.* Water chemistry Miglarese, J. V.* Project management, invertebrate identification Nimmich, T. A. Fish and stomach contents identification; data reduction O'Rourke, C. B. Invertebrate identification; data reduction Roland, E. C. Invertebrate identification; data reduction Sedberry, G. R.* Fish identification; community and food habits analysis Stapor, F. W. Physical habitat description Steele, G. H. Technical support Stender, B. W. Cruise logistics; larval, juvenile fish identification 282 Table 9.1 (Continued) Van Dolah, R. F.* Project Coordinator, project management; community analyses Wenner, C. A. Fish community analysis (review) Wenner, E. L.* Invertebrate identification and community analysis Asterisk (*) indicates primary responsibility for data interpretation and written contributions to final report. 283 Table 9.2. Project personnel from Georgia Coastal Resources Division and their areas of responsibility. NAME AREA OF RESPONSIBILITY Ansley, H. L. H.* Cruise logistics; diver Baisden, V. W. Diver Blizzard, D. Invertebrate identification; diver Boothe, B. B.* Invertebrate identification; diver Brigdon, L. Secretarial support Cowman, C. F. Diver Harris, C. D. Demersal and pelagic fishes; diver Hutchinson, J. Diver Kinsey, C. L. Diver Kroscavage, J. B. Diver Lang, G. M. Diver Mahood, R. K.* Project Coordinator; project management; diver Nicholson, F. L.* Invertebrate identification, diver Olsson, S. P. Diver Phillips, J. Project management Reimold, R. J. Project Leader, project management Shipman, S. 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